Austin Allergy Blog

Prepare for Summer

Sat, 12 May 2012 08:36:44 -0500

Summer is a time for relaxation, when hopefully everyone’s schedule slows down for a while. Even the plants take a break, and many stop producing pollen during the warm months. In fact, the summer is often the best time for most allergy sufferers, and the main pollens found this time of year are the grasses (see the Austin allergen calendar here). However, just because there are fewer airborne allergens doesn’t mean you won’t experience some allergy issues. In today’s blog, I’ll discuss some of the potential pitfalls summer brings to people with allergies.

First, a little more about grass allergy. There are approximately 1200 species of grasses in North America but only about 20 cause allergies. Here in Texas, grasses pollinate from the spring through the fall with the highest levels in June, July, & August. Pollen counts can become very high when heavy spring rains and windy conditions abound (like we’ve had this year), causing traditional symptoms like itchy watery eyes, stuffy nose, sneezing, and drainage. Occasionally, some grass-allergic patients also have skin reactions when they come into contact with grass. During the summer, allergic individuals should avoid being outdoors, especially when the lawn is being mowed or when pollen counts are highest (usually in the morning).

In the summer, we also get to enjoy many seasonal eats; however, for a lot of pollen-allergic patients, many fruits and vegetables also cause them reactions. That’s because various fresh produce share similar proteins with plants that release pollen and therefore cross-react, causing a condition called the Oral Allergy Syndrome. The most common cross-reactions include: ragweed pollen & bananas, cantaloupe, and green peppers; grass pollen & tomatoes, oranges, and peaches; and birch tree pollen with apricots, avocados, and apples. Symptoms include itching or burning in the mouth, tightness or a sensation of swelling of the tongue or throat, and occasionally eye/nose/skin reactions.

Stinging insects are also more prevalent in the summer, and venom-allergic allergic individuals need to be careful whenever they’ll be spending a considerate amount of time outdoors. Recommendations such as not wearing bright clothing or perfume & cologne when outside may prevent attract bees; similarly, sugary foods & drinks may attract insects, including the stinging kind, so refreshments should be consumed quickly and not left out for long periods of time. However, these precautions may not completely prevent an encounter, so having antihistamines and (if a life-threatening reaction can occur) self-injectable adrenaline are important to have on hand. For more information on stinging insects, see my previous blog here.

Going in the water may also cause allergic reactions in some. Chlorine from pools have been reported to cause contact hives in some patients, and when in very high concentration can cause an irritant dermatitis in many who have sensitive skin. Similarly, chorine has been shown to be linked to asthma; in one study, every 100 hours spent in a pool increased the risk of having or developing asthma one to two hundred fold. While the current data is not enough to discourage swimming in chlorinated pools, people with allergies & asthma should be careful if they will be spending a lot of time at the pool this summer.

Water can also cause a variety of skin problems as well. In some patients, “aquagenic urticaria” results from contact with any water leading to a painful or itchy reaction; this is sometimes worsened by the temperature of the water or chemicals within it. Click here to see a report of a patient with this rare condition. In some patients, diving into cold water causes hives; this condition called “cold urticaria” can occur with any cold exposure, but severe, sometimes life-threatening reactions occur most often after plunging into cold water (see here for a report on this condition). For more information on aquatic skin conditions, see my previous blog here.

The sun can also cause rashes as well. Of course, the most common skin reaction to excessive sun is a sunburn; this results from damage due to ultraviolet (UV) radiation which results in inflammation. In some individuals, the inflammation is so intense it causes solar dermatitis, a bumpy itchy rash that occasionally becomes chronic. Sometimes things that get on the skin will cause a reaction when activated by the sun; this condition called a photoallergic reaction can be seen to ingredients in cologne/perfumes, lotions (including sunscreens), soaps, and ingested items such as foods and medicines. A rare condition called “solar urticaria” causes hives with light exposure.

Summer is also the season to spend time in the garden, and for folks allergic to poison ivy, it can be a difficult time. Poison ivy and its relatives cause Rhus dermatitis, an allergic contact reaction that occurs after repeated exposure resulting in a streaky red itchy rash that sometimes blisters. The sap from these plants, called urushiol, binds to the skin and in sensitized individuals, summons inflammatory cells from the immune system to the area of contact; these cells take some time to arrive and begin the inflammatory response which is why the reaction shows up hours following exposure and is called a delayed allergic reaction. For more information on poison ivy, see my previous blog here.

Summer also means camping, picnics, and cookouts, and for patients with allergies & asthma, smoke from barbecues and campfires can sometimes trigger reactions. Fumes from a charcoal or wood fire mainly consist of carbon particles (ash), water vapor, and chemicals (used to start the fire or made during the combustion process). While these substances don’t often cause an actual allergic response, they can irritate people with allergies & asthma that already have inflammation in their respiratory tree. Carbon monoxide can also lead to poisoning in areas that are not well ventilated. Smoke inhalation should therefore be avoided as much as possible.

Even the ballpark is not always a safe place for allergic individuals. We mentioned before how some seasonal foods are sometimes a concern for patients with allergies; for peanut-allergic children, baseball season also brings increased exposure to these potential triggers. Increased air travel during the summer months also means more encounters with peanuts. For patients with food allergies, having an action plan along with self-injectable epinephrine is helpful and may prevent severe reactions. To learn more about peanut allergy, check out this page from the Food Allergy & Anaphylaxis Network.

Summer can be a wonderful time of the year! The kids are out of school, we get to take time off and relax and travel, and we get to enjoy certain activities and foods that we don’t have the rest of the year. But just because summer means less airborne allergens in the environment doesn’t mean you can let your guard down, especially if you have allergies. A little preparation and planning can go a long way to preventing reactions and letting you have a little fun in the sun this year!

If you need help in preparing for summer allergies, feel free to contact us.

J. Alex Martinez, M.D.

When A Sore Throat Needs Antibiotics

Sat, 21 Apr 2012 08:33:55 -0500

Sore throats are common; after all, the throat is a gateway to many important inner systems and is in constant contact with the outside world. Irritants like smoke & dust, post-nasal drainage from allergies, and multiple viruses can inflame the throat and cause pain, but all of these conditions tend to resolve on their own without medical intervention. So why do doctors recommend you come to the clinic for a sore throat? In this week’s blog, I’ll review what Strep throat is and why physicians are so careful not to miss it.

First, a little bit of anatomy. The pharynx includes multiple structures in the nose & throat, especially the area immediately behind the nasal and oral cavities as well as the area above the voice box. The pharynx shares duties for the respiratory as well as the digestive system, helping direct both air & ingested items down the correct channels. Inflammation/infection in this area is called pharyngitis; when due to a Strep infection, it is called Strep pharyngitis or just Strep throat.

The pharynx is lined by a circular cluster of immune glands called Waldeyer’s ring; similar to lymph nodes, these tissues are part of the immune system and are strategically located to monitor and guard this entry point and prevent toxic and infectious agents from infiltrating further. The tonsils & adenoids are part of this ring but it is the tonsils (because of their location behind the tongue) that are most often affected by infection.

Streptococcus is a group of spherical Gram-positive bacteria that cluster in chains when viewed under the microscope. Strep can cause many types of infections, but the type that causes most cases of Strep throat is Group A Strep (GAS) also called Strep pyogenes. These bacteria have many characteristics that make them more likely to cause disease, including a capsule that surrounds the microbe and protects them from engulfing by white blood cells as well as M proteins on the outer layers that allows the bacteria to attach to human cells easier. Although these M proteins give GAS more disease-causing capabilities, they are also their weakest element since our immune system can construct antibodies against them.

Obviously the main symptom of Strep throat is pain; other symptoms include fever, enlarged lymph nodes, and patches of pus on the tonsils. In some patients, headache, nausea/vomiting, and muscle aches are also seen. In most cases, the incubation period is between 1-3 days and the infection is usually spread by close contact. The presence of cough, runny nose, red eyes, and diarrhea makes it more likely the illness is a viral infection rather than Strep throat.

The diagnosis of Strep throat can often be made from the patient’s history and physical exam; however, a throat culture is the gold standard to make certain. In the past, cultures could take 1-2 days to supply the desired information, possibly delaying treatment. Now with the availability of rapid-Strep tests, the results are known in minutes and antibiotics can be started if necessary. Individuals without sore throat and fever should not be routinely tested since a significant percentage of the population are “carriers” of Strep pyogenes without infection.

Given the rise in bacterial resistance seen in the last few years, antibiotics should not be prescribed unless the diagnosis is fairly certain. Another reason why it is important not to miss a Strep throat infection is that untreated infections are often associated with serious consequences, including rheumatic fever, inflammation of the kidneys, scarlet fever, and toxic shock syndrome. Rheumatic fever occurs when antibodies directed against the M protein on the outside of the bacterium cross-react with certain tissues in the body, especially skin, joints, heart, and brain. The illness develops 1-3 weeks after a bout with Strep throat and most often is seen in children aged 6-15. For more information on how rheumatic fever develops, click here.

Scarlet fever occurs during an active untreated infection with Strep pyogenes and is due to release of a bacterial toxin. Before the era of antibiotics, scarlet fever was feared because of its many complications, including glomerulonephritis (inflammation of the filtrating portions of the kidney potentially leading to renal failure) and endocarditis leading to heart valve disease. Along with sore throat and fever, scarlet fever is associated with a bright red “strawberry” tongue as well as a characteristic red & rough-textured rash which begins on the chest or armpits and peels a few days after appearing.

Avoidance is always the best way to prevent illness like Strep throat. Close contact such as sharing utensils or drinks should be avoided with persons that have sore throat. It is also recommended that people not share toothbrushes and wash their hands often. To strengthen the immune system, a nutritious diet, plenty of sleep, and regular exercise is also recommended. For smokers, discontinuing tobacco use is also advised.

The symptoms of untreated Strep pharyngitis can resolve on their own within a few days; as described above, to avoid additional medical complications, it is imperative to make the diagnosis of Strep pharyngitis and treat it with antibiotics. Studies have also shown that antibiotics shorten the duration of the acute illness by about 24 hours, and it is usually safe for children to return to school 24 hours after starting antibiotics. Antibiotics also reduce the transmission of the infection within families and schools.

The antibiotic chosen to treat Strep throat is most often penicillin since it has coverage against GAS and it is safe, relatively inexpensive, and readily available. Cephalosporins (antibiotics distantly related to the penicillins) can also be used against Strep throat. For patients who are allergic to the penicillins, the macrolide antibiotics (like erythromycin) are recommended. Even though antibiotics can treat the infection and prevents many complications, it does not seem to reduce the risk of glomerulonephritis, so monitoring is still recommended.

There are over 11 million cases of pharyngitis diagnosed in the U.S. every year; most of these will not require medical attention and will resolve on their own. However, Strep pharyngitis can have serious consequences if left untreated, so it is important not to ignore a sore throat, especially if it is accompanied by fever and white patches on the tonsils. GAS can be easily treated with antibiotics, but every effort should be made to ensure that a bacterial infection is present to avoid resistance. Recurrent Strep pharyngitis may require surgical intervention.

If you develop a sore throat and are worried you may have Strep, please feel free to contact me.

A. Alex Martinez, M.D.

Snoring & Your Health

Sat, 7 Apr 2012 18:11:58 -0500

We humans spend about one-third of our lives sleeping, and for many reasons, the quantity & quality of sleep isn’t always the best. Snoring is one of the reasons our sleep is disturbed, an acoustic nuisance that affects both sleeper & partner alike. It is estimated that about 40% of the adult population snores, and structural anatomical reasons are almost always implicated. Since the 1970’s, it has become clear that, aside from sleep disturbance issues, in some patients snoring can have more serious health consequences. In this week’s blog, I’ll review how snoring occurs and when someone’s snoring requires a medical evaluation.

Snoring is the sound produced by the vibration of anatomical tissues in the upper airways as air passes in & out during sleep. The sound can be generated by any structure that isn’t supported by cartilage, including the soft palate (the roof of the mouth), the uvula (the “bell” that hangs in the back of the throat), and the tissues of the throat to the level of the vocal cords. Because so many areas can vibrate and make sound, the approach to decrease snoring may not be a “one-size-fits-all”.

Snoring occurs frequently but estimates on how prevalent it is vary greatly. Part of the problem is that snorers rely on their bed partner to describe their snoring; other factors like diet & alcohol consumption also cause night-to-night variability. Data suggests it is more common in men than in women, and some conditions are associated more with snoring, including nasal polyps & pregnancy. It may also be hereditary to some degree, and although some studies suggest that snoring may decrease with age, this may be related more to the loss of a bed partner or change in the perception of snoring rather than an actual decrease.

Snoring is now included in a spectrum of breathing abnormalities called Sleep-Disordered Breathing (SDB). Primary snoring is the most common aspect of SDB, and while it occasionally has no ill effects on the snorer, it can cause a feeling of fatigue upon waking, daytime sleepiness, poor work performance, and difficulty concentrating. These symptoms often prompt a sleep study that investigates whether snoring is associated with frequent awakenings and a decrease in oxygen intake during the night.

Through a sleep study, primary snoring is sometimes reclassified as Upper Airway Resistance Syndrome (UARS) or Obstructive Sleep Apnea (OSA). In UARS, sleepers have a breathing pattern called crescendo snoring where snoring increases in intensity & volume followed by a short period of unconscious waking that causes the snoring to stop for 3-4 breaths, then the pattern is repeated. During those episodes, unlike in OSA, there is no evidence of decreased oxygen in the bloodstream.

OSA, on the other hand, does exhibit cycles of partial or complete airway obstruction with decreased oxygen levels; having at least 5 obstructed breathing events per hour during a sleep study confirms the diagnosis of sleep apnea. The patient must also have either excessive daytime sleepiness or at least 2 other features, including choking or gasping during sleep, recurrent awakenings from sleep, feeling unrefreshed from sleep, daytime fatigue, or poor concentration.

The concern with OSA is that those periods of low oxygen in the circulation puts a lot of stress on other parts of the body and can lead to serious health effects. Studies have shown that episodes of snoring are often associated with an increase in blood pressure; similar results have been seen between snoring & cardiovascular disease (heart failure, irregular heart beats, and heart attacks) as well as stroke. OSA has also been associated with diabetes, depression, and worsening Attention Deficit-Hyperactivity Disorder (ADHD).

The treatment for snoring is aimed at discovering the cause. A medical consultation should assess various risk factors such as alcohol consumption and weight gain. A history of recurrent upper respiratory infections (such as tonsillitis) can be important, as well as asking about nighttime & daytime symptoms. The doctor should also examine the nose for possible causes of blockage such as allergies, a deviated septum, or nasal polyps. The exam should also assess the dimensions of the throat & note the presence or absence of excess tissue. A sleep study may also be needed to see if episodes of unconscious waking and low oxygen occur while sleeping.

Treatment for snoring can be divided into nonsurgical & surgical. Non surgical treatments include lifestyle modifications such as weight loss, avoidance of alcohol and sedatives, and positional training. Treating the nasal congestion with medications is also helpful, as are nasal dilators and oral appliances that cause protrusion of the mandible and allow air to flow in & out easier. Studies have shown that when these devices are constructed by dentists with specialized expertise, the appliances are relatively comfortable and decrease snoring.

Even for snorers that do not suffer from low oxygen levels when sleeping, machines that ‘push” air past obstructed tissues can help with snoring. Continuous Positive Airway Pressure (CPAP) is the most common and studies suggest that, especially when daytime sleepiness is a problem, this device can help. Cost and comfort are the main drawbacks, so most patients with only primary snoring may not feel the device is for them.

Surgical treatments can offer a quick-fix for many snorers since the procedure can alter the anatomy to facilitate air flow through the nose & throat. Studies indicate that snorers often have deviated septa or other forms of nasal congestion in greater numbers compared to non-snorers; despite this, little evidence is available that treating nasal obstruction surgically by fixing the deviation or reducing the turbinates improves snoring. Therefore, unless the blockage in the nose is causing other medical issues, at this time, nasal surgery for primary snoring is not recommended.

Throat surgery is also performed for snoring. Palatal implants inserted into the soft part of the roof of the mouth under local anesthesia can help to stiffen the area and prevent it from vibrating during sleep to reduce snoring. Other procedures are more aggressive and include injection snoreplasty where a scarring agent is injected to shorten and tighten the roof of the mouth, uvulo-palato-pharyngo-plasty (UPPP) where a large area at the back part of the roof of the mouth is removed, laser-assisted uvuloplasty done under local anesthesia using a laser to remove excess tissue in the throat, and radiofrequency ablation that uses a special probe which “heats up” the redundant tissues causing these to shrink and harden.

A good night’s rest is important for many reasons, and snoring can prevent you or your sleeping partners from getting adequate slumber. In the past, snoring has been the fodder of many jokes, but it is now known to be associated with possible health hazards. There are many physiological and anatomical reasons that can cause snoring, so a medical evaluation may be indicated. In addition, consultation with an ear-nose-and-throat surgeon can be helpful.

If you or a loved one snores and it’s affecting your sleep, please feel free to contact me.

A. Alex Martinez, M.D.

For more information on sleep disordered breathing, click here.

Vertigo & Balance

Sat, 31 Mar 2012 10:27:24 -0500

Vertigo (a word that comes from the Latin verto, to spin or whirl) is a sensation of revolving motion despite being stationary. Because it causes dizziness and a loss of balance, it is often associated with unsteady gait, nausea, vomiting, sweating, and blurry vision. Vertigo occurs when the brain gets mixed signals regarding the body’s equilibrium, often due to an inner ear problem. It is different that being light-headed or feeling faint since these do not involve a feeling of movement and often improve with lying down.

The body gets information of where we are in three-dimensional space from three main areas: the eyes, the inner ears, and nerves in the periphery. These all send signals to the brain regarding our direction and speed, and together these parts make up our vestibular system which is responsible for balance & equilibrium. All three areas are important, and problems with any of them can result in feeling “off kilter”; however, confusing signals from one area can sometimes be countered by information from the others, delaying medical diagnosis and treatment.

Vertigo primarily starts in the inner ear where a labyrinth of structures reside. For example, the semi-circular canals are arranged spatially at right angles to one another in an X-Y-Z configuration; this balance apparatus senses changes in motion and relays the information to the brain. The canals are filled with a gelatinous fluid which moves as changes in position and direction occur; the movement stimulates hair like projections inside the canals which generate a nerve signal. This area, therefore, provides data on dynamic position.

At the end of the canals are bulbous structures called vestibules which house the otolith organs consisting of inorganic crystal “stones” that reside on additional sensory hair-like projections. After being at rest, motion causes the otoliths (seen red on the picture to the right) to “roll” around over the hair-like projections (seen in blue), causing these to “bend”; the deflection then generates a nerve signal, telling the brain that a static positional change has occurred. For more information regarding information generated by the semi-circular canals and otolith organs, see here.

Most causes of vertigo involve inner ear problems. Benign Positional Vertigo occurs when some of the otoliths leave the vestibule and accumulate in the semi-circular canals. These “canaliths” stimulate the sensory hairs in the canals like they normally would in the vestibule; this sends confusing signals to the brain and cause vertigo. Labyrinthitis is inflammation of the structures that make up the vestibular system, most often due to a virus but occasionally caused by bacterial infections; the inflammation also causes vertigo. Ménière's Disease which causes vertigo, ringing in the ears, and hearing loss is believed to be linked to endolymphatic hydrops where excess fluid in the labyrinth exerts pressure which leads to the symptoms.

The pressure in the inner ear is equalized by the Eustachian tube; dysfunction of this structure allows pressure and sometimes fluid to build up in the inner ear which can result in vertigo. Allergies, colds, and sinusitis all can cause tissue swelling with blockage of the Eustachian tube. Similarly, inflammation of the nerve that carry the signal from the inner ear to the brain can result in vertigo. Vestibular neuritis, usually following a viral infection, is one such example. An acoustic neuroma is a non-malignant tumor arising from the cells that cover the vestibular nerve; these most often present with hearing loss and vertigo.

When the cause of the vertigo involves a structure outside of the inner ear, it is referred to as nonvestibular vertigo. Possibilities include disturbances of the muscles that move the eyes; neurological problems of the brain (cerebellum), spinal cord, or peripheral nerves (such as MS); migraines; intoxication with alcohol or medications like salicylates and quinine; anxiety (phobic attacks of vertigo); hyperventilation; metabolic disorders; and cardiovascular disease.

The treatment for vertigo depends on the cause. If the Eustachian tube is blocked and pressure in the inner ear is the cause, then medications that decrease swelling and inflammation are indicated. Bacterial infections can be treated with antibiotics and viral infections may benefit from symptomatic treatment with medicines such as meclizine (Antivert®) which seem to stabilize the balance center and suppress the confusing signals being sent to the brain. Sedatives are sometimes also helpful although the side effects make these difficult to take during the day.

Benign positional vertigo can be treated fairly successfully in one of two ways. The first involves doing a series of head rotations and positional changes that move the mineral debris in the semi-circular canals out; called the Canalith Repositioning Procedure, it can be done in a doctor’s office in about 10-15 minutes and may be effective in up to 80% of cases. Physical therapy can also provide a series of ongoing exercises that are done in the patient’s home for 10 minutes twice daily; these help the patient adapt to various positions and improves balance; this treatment is also very effective.

In rare cases, surgery may need to be considered for some patients with unremitting vertigo. A labyrinthectomy destroys the balance organ of the affected inner ear in order to stop the mixed signals being sent by it. Unfortunately, the procedure also destroys the hearing on the affected side. Immediately after the procedure, there is acute vertigo due to the loss of signals from one side, but the brain usually compensates and learns to interpret the information coming from the remaining side. The operation is usually performed through the ear with no incision or through the mastoids using an incision behind the ear.

Being in balance can prevent injury, and our bodies rely heavily on information received from the inner ear, the eyes, and the peripheral nerves to accurately place us in three dimensional space. Patients who suffer from vertigo feel as if their world won’t stop spinning, and all they want is to “stop the ride”. Identifying the cause of the vertigo is important so that the appropriate treatment is initiated. Consultation with an Ear-Nose-Throat surgeon can also be helpful.

If you think you may be suffering from vertigo, please feel free to contact me.

A. Alex Martinez, M.D.

For more information on vertigo, click here.
For visual illusions that appear to be moving, click here.

Allergy to Snakes?

Sat, 17 Mar 2012 21:45:54 -0500

Since antiquity, snakes have been regarded as evil, malevolent creatures. Maybe it’s due to their appearance: they have no neck or limbs, their eyes never blink and therefore their expressions never change, they have forked tongues, and they look slimy. Maybe it’s the way they behave: they are silent, stealthy hunters who slither and strike quickly, and kill maliciously with poison. Snakes also inhabit dank forest floors or lurk in tall grass, unseen until it’s too late. It isn’t difficult to see why snakes are loathed almost more than any other creature on earth, our hatred for them is almost instinctual.

This weekend we celebrate St. Patrick, patron saint of Ireland; legend holds that he heroically saved the Emerald Isle from a plague of snakes approximately 1500 years ago. However, all evidence suggests that post-glacial Ireland never had any snakes. The icy ocean waters would have prevented any migration of cold-blooded reptiles from Britain or anywhere else, and the fossil record has not uncovered any proof that snakes ever inhabited the island. In reality, the story of St. Patrick banishing the “evil snakes” our of Ireland most likely represented the symbolic driving out of the old pagan ways, supplanting these with Christianity.

Although the majority of snakes are not venomous and kill their prey by constricting them instead, being bitten by a snake is one of the biggest fears humans possess. Venomous snakes can be found in every continent except Antarctica; snakebites and the resulting envenomation are primarily used for capturing prey but can also be used in self-defense. Some venoms are potent enough to cause severe and painful injury to humans, and occasionally even death. However, fewer than one in 37,500 people are bitten by venomous snakes in the U.S. each year (7-8,000 bites per year), and only one in 50 million people will die from snakebite (5-6 fatalities per year).

Snake venom is essentially highly modified saliva; it includes numerous toxic proteins that can have various effects in the body of a victim, including immobilization by affecting nerve and muscle impulses, preventing blood from clotting, and lowering blood pressure. Some venoms also include enzymes that aid in digestion of the prey. Venom is made in specialized salivary glands behind the eyes and are stored in special sacs before being channeled through tubular fangs as the snake bites.

The outcome of snake bites depends on numerous factors, including the species of snake, the area of the body bitten, the amount of venom injected, and the health of the unfortunate victim. In the U.S. the largest volume of venom ever recorded was milked from an Eastern Diamondback Rattlesnake and measured about 850 milliliters (over 3.5 cups!). This venom is also one of the most toxic of U.S. snakes, though it is about 10 times weaker than the most potent venom found worldwide. Most experts agree that the strongest, most toxic venom (as tested in mice) comes from the inland Taipan snake from Australia.

The most common effect of a snakebite is (understandably) overwhelming fear, panic, and emotional distress. This may lead to hyperventilation, nausea, vomiting, diarrhea, elevated heart rate, dizziness, cold clammy skin, and feeling faint. At the bite site, fang marks and bleeding can be seen associated with pain and/or a burning sensation. Occasionally, a forceful bite may even cause tearing the flesh. Even with “dry” snakebites when no venom is injected, infection from various bacteria in the snake’s mouth or the victim’s skin can spread quickly and potentially result in death. For more general symptoms following a snakebite, click here.

Due to the various toxins found in snake venom, bites which result in envenomation cause severe and significant local tissue destruction. Redness and swelling leads to blistering and increased pressure within the tissues which eventually can cut off the blood supply to the area and lead to cell death and necrosis. As more and more muscle tissue dies, a condition called rhabdomyolysis ensues, and breakdown products like myoglobin are released from dying muscle cells into the bloodstream. These compounds can damage the kidneys which, coupled with low blood pressure, can result in kidney failure. As the venom and its effects spread throughout the body, more life-threatening symptoms develop, including rapid breathing and heart rate, severe internal bleeding, and respiratory and cardiac failure. The victim eventually succumbs and dies.

The proteins found in venom not only exert a direct toxic effect on various tissues, they also elicit an immune response. Envenomation that is survived leads to the development of protective antibodies, a fact that may have been recognized by various ancient cultures. King Mithridates (132-63 B.C.) protected himself against poisoning from his enemies by taking up small doses of poison and building up resistance. Developing humoral immunity against snake venom was apparently practiced by the Chinese as well as the Marsi people in the Abruzzi Mountain region of Italy.

Repeated exposure to venom (as seen in snake charmers who receive frequent bites) can also lead to production of IgE, the allergic antibody. In this case, rather than protection from antibodies that neutralize the venom, severe (even life-threatening) allergic reactions can occur. Surprisingly, the development of IgE can occur even without being bitten, and various researchers who merely handle venom have experienced full-blown anaphylaxis following their first envenomation.

Severe allergic reactions can also occur to antivenom. Antivenom is produced by milking venom from a given species of snake(s) and then injecting a diluted version into another animal, usually a horse. The animal’s immune system reacts by forming protective antibodies which can then be harvested and administered to humans bitten by the same type of snake(s). Because the horse antibodies are “foreign” to humans, they can elicit an intense allergic response; however, in emergency situations this can be treated and the benefits far outweigh the risks involved with not using the antivenom.

The story of St. Patrick forcing “evil” out of Ireland may be mythology, but it symbolized a change on that island, and it revolved around man’s fear and detestation of snakes. Snakes now are often kept as pets, and while they don’t cause airborne allergies, their bite can cause severe reactions. Increased knowledge about how venom affects the immune system has led to better treatment of snake bites and has significantly decreased the number of people dying from envenomation every year.

If you have any questions regarding this blog, please feel free to contact me.

A. Alex Martinez, M.D.

For more information, check out these links:
Anaphylaxis and the Venomous Keeper: What You Need to Know
The Science Behind Venomous Snake Bites
Venom, Antivenom, and Immunity
How To Prevent and Treat Snake Bites