About Sarskia Flemming

Sarskia has a passion for all things Australian and is a regular blogger on Aussie Blogs. You can find her on Google+, Facebook and Twitter.

Allergies – What Is an Allergy?

There is little good news associated with hearing “you’re allergic”.

Sadly, all too many people know what an allergy is first hand. The itchy eyes, runny nose, skin rash and other symptoms are uncomfortably familiar. But a more accurate medical definition can be helpful, because it’s the first step toward diagnosis and treatment for the right condition.

The definition of allergy derives from a large body of facts. It is a hypersensitive reaction to allergens that produce an allergic reaction. But that definition is circular. What is an allergen? What’s an allergic reaction? Let’s flesh it out.

In a percentage of the population, exposure to otherwise harmless substances called allergens causes a type of white blood cells to produce a biochemical called IgE (Immunoglobulin E). Inside the body, that compound then attaches to mast cells or basophils (more white blood cells). They in turn release histamines, prostaglandins and other compounds. Their overproduction are what create the actual symptoms you feel.

The results of all that activity for an individual vary. The strength and type of reactions will differ from person to person. Some will experience mild to severe asthma. Others develop a skin rash, such as eczema. Still more suffer from the common watery eyes and running nose. Hives, hay fever and even anaphylaxis may occur.

So, an allergen is any substance that will cause a person to experience these allergic reactions. That covers a lot of ground, regrettably.

Such well known environmental entities as pollen affect millions. Many are sensitive to animal dander and dust mites. Some people are allergic to bee or wasp stings. Still others experience symptoms when they come into contact with or consume certain foods, such as milk, peanuts or shellfish.

There is a significant genetic component to being affected, a condition called atopy. But, allergies can be built up over time with repeated or prolonged exposure.

A small amount of dust, for example, may leave an otherwise sensitive person unaffected. But, over time, as more dust mites carried on the particles enter the nasal cavities and sit in the sinuses, they release more and more material. The eventual result can be the familiar rhinitis or runny nose associated with that particular allergy.

Similarly, conjunctivitis (a swelling and irritation of the membranes lining the eyelid) are a common result of exposure to some environmental substances. It is a typical symptom of hay fever, hives and other allergic reactions that are uncomfortable but rarely dangerous.

Still more serious reactions are not only possible, but almost guaranteed in some cases. Certain people are hypersensitive to bee stings. One sting can produce anaphylactic shock, a reaction that can lead to severe respiratory distress, circulatory system difficulty or even death. Onset can be rapid and include drastically lower blood pressure, constricted breathing and severe skin rashes. Fortunately it’s easily treated with epinephrine or cortisone.

Testing for allergies, and treating them, has improved in the past few decades. Though procedures may still be unpleasant and treatments less than perfect, advances have allowed the allergy sufferer to find relief quickly. Cures are few and far between, but symptom relief can be substantial and long lasting.

For millions, that’s good news.

Allergies – What Causes Allergic Reactions?

Two factors are involved in every allergic reaction – the allergen and the person who is sensitive to it.

An allergen is any substance that produces an allergic reaction. But that sounds circular. To flesh it out a little simple science is all that’s needed.

The body’s immune system releases antibodies to anything it views as a foreign substance. Bacteria, viruses and even transplanted organs have a genetic ‘signature’ that doesn’t match that of an individual. So, they’re seen as something foreign, something the body needs to eliminate.

To do that, white blood cells move to an area where the foreign substance is located. In the case of an allergen, those are usually proteins such as pollen or those found in certain foods like milk or peanuts. The white blood cells then cause the release of histamines and enzymes into the surrounding fluid to envelop the foreign protein.

But there enters the second factor in an allergic reaction: you.

For reasons not fully clear but having a known genetic factor, the immune system of some individuals overreacts. It produces too much for too long of these allergen fighting substances. The result is the familiar watery eyes, itchy skin, runny nose and other allergy symptoms.

That sensitivity isn’t necessarily a fixed amount, either. Repeated exposure over a period of time can cause a ‘ramp up’ to an allergic reaction. As an example, consider an allergic reaction to dust.

We inhale dust all the time. Some people can do this for a lifetime and never produce anything more than an ordinary sneeze. The body filters out the material and all goes on as normal. But, the dust also carries dust mites, who shed proteins in their waste. Over time, some people will gradually generate an overly strong immune system reaction to those proteins.

The underlying genetic factor has not been precisely identified. But, statistically, it is known that allergies tend to run in families. Still, there are environmental factors – beyond the mere presence or absence of allergens – that play a role as well.

For example, breast fed babies tend to have fewer allergies, even within families known to be at greater risk. For the first few weeks after birth, the baby’s immune system is not yet fully developed. Mothers aid in that process by delivering antibodies during feeding that the child doesn’t yet create on its own.

It might appear at first blush that stomach acid would destroy the helpful antibody proteins given in breast milk and colostrum. But, unlike adults, babies produce much less stomach acid. So, a percentage of the prolactin and other helpful compounds survive the infant’s digestive process. The process is also helped by the fact that immuno-proteins are glycosylated, a kind of wrapper that helps protect them from being broken down in the child’s stomach.

The full details of allergic reactions are still a matter of ongoing research. But, there are many things a person can do to minimize his or her risks. Before showing how, we need to know a little bit more about how the immune system works…

Allergies – What Are Hives?

Hives (allergic urticaria) are red, itchy bumps near the surface of the skin. Like many other allergies, they are the result of overproduction of histamine. That reaction can be produced by a wide variety of things.

In many cases, hives are the consequence of a food allergy. Eggs, peanuts, shellfish, milk and other foods can cause hives. The bumps aren’t generally painful but the itchiness is uncomfortable and the hives can be made worse by scratching.

They may also be the result of a drug sensitivity. Penicillin shots and antibiotics may produce them. Blood pressure control medicine can cause hives. But even simple aspirin or ibuprofen are the culprit among some allergy sufferers.

In still other patients, airborne or contact allergens like pollen and animal dander can produce the characteristic red swellings. Insect stings, such as those of bees and wasps, typically produce breathing difficulty for those sensitive to the venom. But hives are far from unknown in this case, as well.

In short, any allergen that produces more common allergy symptoms can also produce hives. Conjunctivitis (inflammation of the eyelid membrane) and allergic rhinitis or hay fever (an inflammation of the nasal membranes) are more typical. But hives are similar in that they result from overproduction of histamine and other cytokines that produce swelling.

What To Do?

Prevention is always the best option, when possible. Beyond keeping the environment relatively free of allergens and foregoing certain foods, though, there is no ‘cure’, only symptom treatments.

Itching and swelling can be handled by application of a cold compress. A cool shower may bring only temporary relief, but sometimes ‘temporary’ is long enough. Avoid scratching and wear clothing that doesn’t irritate the area further.

Non-prescription antihistamine medications like Benadryl (diphenhydramine) or Claritin (loratadine) can help reduce hives. The latter has the added benefit that it doesn’t typically cause drowsiness.

Prescription medications are sometimes just a stronger dose of the same substances. But some medicines contain different compounds. Atarax (hydroxyzine) and Allegra (fexofenadine) are two frequently prescribed alternatives. In more severe cases, physicians may suggest an oral corticosteroid such as prednisone.

Since there are many conditions that can produce red, swollen bumps (such as acne, for example) it’s important to know when you have hives. Only a professional diagnosis can produce a definitive answer. But there are common things to look for.

Allergies tend to run in families, though individuals don’t always have the same sensitivity in kind or degree. Also, learn to distinguish between urticaria and contact dermatitis from poison ivy. The latter is the result of contact with the plant’s oil and it spreads by moving the oil over the skin. Hives are produced from the inside.

For those who are especially sensitive, it can be beneficial to have an EpiPen or similar device on hand. These allow the self-administration of a controlled dose of epinephrine to treat anaphylaxis.

Allergies – The Immune System

An allergy is the result of an overreaction by the body’s immune system in the presence of an allergen. But how does that work, exactly? Knowing that helps one understand what’s happening when you suffer that runny nose, itchy rash or stomach upset.

An allergy is actually a category of hypersensitivity. Substances (called allergens) that most people would suffer no problem from cause others’ immune systems to go into overdrive. Here’s what’s happening ‘under the hood’…

There is a system in the body that runs parallel to the blood vessels, called the lymph system. It plays a major role in keeping disease and infections at bay. Much of that is concentrated in the lymph nodes, part of the system that produces lymphocytes, cells that attack disease.

Tonsils, the appendix and others are also lymphoid tissue. But there is so-called lymphoid tissue elsewhere, including most importantly the bone marrow and the thymus (an organ just behind the breastbone). It is the thymus that produces T cells, a type of white blood cell. These T cells play a key role in allergies.

As a result of many articles written on AIDS over the years, the name of these cells is widely recognized. But what do they do?

They have several functions, but one of the primary ones is to patrol the blood and lymphatic fluid looking for foreign substances. Every cell in our bodies has a genetic ‘signature’ that is unique to us. Anything, like a bacteria or virus, that has a different signature is seen as a foreign substance and a candidate for removal.

Some T cells merely mark those foreigners as foreign, then the substances are removed by phagocytes or other mechanisms. Some T cells communicate with B cells to help them do their job in the immune system. And some T cells directly attack those foreign proteins.

Mast cells (a type of white blood cell), for example, in conjunction with basophils (another type) rush to the site of such an invader. On cue, they cause biochemicals such as histamines and prostaglandins to flood the area. That helps engulf the invader, neutralizing it. The ‘package’ is then carried away and out of the body.

But that reaction can go too far. If an otherwise harmless substance gets marked for destruction, the whole process is carried out unnecessarily. If the reaction is larger than needed, too much histamine and other substances can be released.

In either case, the result is an allergic reaction.

The runny nose from a nasal inflammation (allergic rhinitis), red and watery eyes from inflamed eyelid membranes (conjunctivitis), red skin welts (hives) or other common allergy symptoms all follow from those processes. The body is overreacting, causing the immune system to go into hyperdrive and cause harm to itself.

Building up the immune system is one major key to good health. But like anything, balance is essential. Too weak a reaction would leave us vulnerable to disease. Too strong a reaction creates an allergy.

Allergies – Pollen and Mold Allergy

During much of the year, plants produce pollen. Mold knows no season and may occur anytime. Plants release pollen in order to fertilize other plants. Not all of those particles reach their intended targets. Some enter the airways of people. The same goes for mold, which can find its way into the nose or mouth through many routes.

The proteins in these plant substances are viewed by the body as foreign invaders. They stimulate the immune system to release antibodies that cause the body to produce histamine. Overproduction leads to well known allergy symptoms. Asthma and wheezing, allergic rhinitis and conjunctivitis (inflammations of the nose and eyelid membranes, respectively), and other symptoms are a common result.

Since pollen grains can be carried by the wind for hundreds of miles, getting away from the area isn’t usually an option. Molds can build up in any humid area of the house. Both these common allergens can’t be eliminated from the overall environment. But they can be minimized in your environment and, more specifically, your body.

Pollen Management

Since pollen levels vary during the day, changing your habits can help control the level of exposure. They’re likely to be higher in the early morning, from about 5 am – 10 am. They’re also affected by humidity levels. Rain or even high humidity can keep pollen down closer to the ground. They don’t fly as well in moist, heavy air.

Keeping the windows closed can help, since it prevents the pollen grains from wafting in through the screens. Air conditioners fitted with good filters are preferable to window or attic fans for cooling. Drying clothes outdoors leads to increased pollen indoors, since the grains get attached to the clothing which then may come into close contact with the nose and mouth.

Mold Management

Mold grows in a humid environment. While humidity helps keep the level of pollen down outdoors, it increases mold inside. An air conditioner/dehumidifier is helpful. Regular cleaning is also helpful to ensure that moisture doesn’t stay on surfaces that come into contact with your hands, then the nose and mouth. Anything that gets on your hands and isn’t washed off will sooner or later end up in your airways.

Keeping the bathroom and kitchen clear of mold is relatively easy with modern sprays. Be sure to cleanse your hands well after cleaning up, though. Dry the hands well after cleaning thoroughly.

Medications

When you’ve undertaken all reasonable preventative measures, but still have an allergic reaction, medication can come to your aid. The underlying condition isn’t cured, but symptom relief can be substantial.

Antihistamines like Benadryl (diphenhydramine) are one effective treatment. They counteract the overproduction of histamine that leads to swollen nasal passages and other common symptoms. Corticosteroids are another option. They help reduce nasal inflammation and minimize excess mucous production. Overuse can lead to bad side effects, however.

Summary

For any allergic condition which persists for more than two weeks, a visit to a specialist is in order. There are no cures for allergies, but proper diagnosis, management and treatment can substantially reduce the unpleasant effects.

Allergies – Insect Stings and Allergic Reactions

Insect stings are never pleasant. But for some, the discomfort goes beyond the moderate pain that dissipates in a few hours. Bee and wasp stings and certain spider bites are toxic for everyone. But some individuals are allergic to the venom, producing a much more serious reaction. Official estimates are in the range of 2 million people in the U.S. who are allergic to the venom.

Symptoms may involve swelling of the lips, tongue and throat. In severe cases that can produce difficulty breathing. Anaphylaxis is common in those allergic to bites and stings. The blood pressure drops precipitously, leading to dizziness and possible circulatory failure. The throat can swell to the point that breathing is completely blocked.

Even in less severe cases, wheezing is a common allergic reaction to those sensitive to venom. Itching and swelling at the site are typical.

What To Do?

Fortunately, there are several effective strategies for dealing with these allergic reactions.

Avoidance is always best, but that can be hard to do. Bees are prevalent anywhere flowers are found. Wasps are attracted to sugar solutions, meat and other foods that can be inside or outside the home. Hummingbird feeders, outdoor barbecues and other common elements can attract either. Hanging traps away from these attractions can help.

Spiders are a little easier to avoid, usually. They tend to avoid contact. Keep sheds clean and swept free of webs to encourage them to try their luck elsewhere. Keep a sharp eye out for them in dimly lit areas of the basement or gardening shed.

What should you do when you are bit or stung, anyway?

Only a professional diagnosis can completely distinguish an ordinary reaction to a bite or sting and an allergic reaction. But anytime the reaction goes beyond the normal level of pain and swelling that subside in a few hours, an allergy should be suspected.

Sometimes, of course, you can’t wait that long. If breathing becomes difficult or the person experiences facial or throat swelling away from the site, measures will need to be taken immediately.

When bees release their barbed stinger and fly away, the stinger remains in the skin. It is usually accompanied by all or part of the venom sac and contains tissue that will continue to pump venom after it separates from the bee. Don’t pluck the stinger out. Instead, try to scrape it away. This helps remove the barb and gets rid of the sac without squeezing out more venom. Wasp stingers can be removed by scraping the skin with a sterilized dull knife in the direction opposite the entry.

Then apply ice or a very cold, wet washcloth to the area to reduce pain and swelling. If allergic symptoms persist or grow, have medication on hand.

With spider bites, look for any necrosis (black, dying tissue) that occurs apart from the redness or swelling. If the affected area spreads beyond the puncture site, seek professional care at once.

Antihistamines like Benadryl (diphenhydramine) are beneficial. A topical hydrocortisone cream can help, too. In more severe cases, it will be desirable to have handy an EpiPen or similar device. They allow patients to inject a controlled amount of epinephrine to treat anaphylaxis symptoms. They’re not for everyone, however. Consult your physician first.

Allergies – Immunotherapy Allergy Shots

There are a half-dozen popular treatments for allergy symptoms. Benadryl (diphenhydramine), Claritin (loratadine) and others are well known antihistamines. Decongestant sprays, such as Nasonex, are readily available by prescription. But these treat only symptoms. Allergy immunotherapy attempts to get to the root of the problem – the overactive immune system – and to offer a long-term cure by changing it permanently. In essence, it’s a form of vaccination.

Allergy immunotherapy generally comes in the form of shots taken weekly. The syringe contains a carefully calibrated dose of allergen, such as an extract of ragweed pollen or cat dander, sometimes genetically modified. The goal is to gradually desensitize the immune system. Since an allergic reaction is an overreaction to a substance seen as a foreign invader, the idea is to ‘teach’ the immune system to better distinguish friend from foe.

The treatment is not experimental. It has been in clinical use for several years. But it does carry some possible downsides.

Shots are much more expensive than over-the-counter pills and creams. Since they’re administered by a trained professional allergist they are also frequently more costly than prescription medications taken at home.

They also require making those visits to the doctor, regularly and for a long time. A few weeks to a few months is usually required to calibrate the correct type and amount of allergen given in the shots. Once established, the treatments may go on for three to five years or more. The length varies with each patient, but the goal is more or less to permanently alter the patient’s immune system reaction to certain substances. That takes time.

Allergy shots are also not useful in certain classes of allergy, particularly food allergies. While the treatment might potentially work, the risk of anaphylaxis is considered too high. The shots inject the patient with a substance that produces the allergic reaction. Therefore, there is too great a chance that a food allergy sufferer can have a life-threatening reaction.

On the upside, there is ample clinical evidence from numerous careful studies that support a belief in the efficacy of the treatment. In short, it works. Not for everyone, naturally. But about three-quarters of those receiving long-term treatment do eventually rid themselves entirely of the allergy. For many, even the substantial reduction in symptoms makes the effort and expense worthwhile.

It is effective in treating those allergic to animal dander, dust mite waste and pollen grains. It’s highly useful for those who can’t take or don’t find relief from standard medications. It has been successful at permanently relieving hay fever and may prevent the onset of asthma in children. It has been shown to reduce the odds of an allergic reaction to bee and wasp stings.

For those who suffer severe symptoms, or who simply want to avoid taking pills for the rest of their lives, that is very good news.

Allergies – Home Air Purifiers Reduce Allergens

One effective way to manage allergy symptoms is to reduce the amount of allergens present. For those who suffer from allergies caused by airborne allergens, a home or car air purifier can help do just that.

There are many different types on the market, though, some more effective than others.

Many home air purifiers produce ozone. Ozone is just an oxygen molecule (two oxygen atoms bonded together) with an extra oxygen atom alongside. Since the oxygen molecule is fairly stable, the third atom tends to get knocked off easily. When that happens it becomes what is called a free radical, and it is electrically charged.

Those charged oxygen atoms can harm the lungs. They carry energy and, because it is oxygen, readily participate in lots of biochemical reactions. Those reactions aren’t always beneficial. In extreme cases, they can increase the odds of lung and skin cancer. For some, asthma symptoms can be worsened by exposure to large amounts of ozone.

But the amounts produced by the average home air purifier are much lower than these dangerous levels. At most, some truly sensitive people can smell a hint of ozone in the air. The purpose of the ozone is to combine with potentially harmful particulates in the air and then move them to the walls or back to the air purifier.

Many good home air purifiers do their good work by creating a low intensity electric charge on metal plates. The purifier then uses a fan to move air around and the dust, animal dander and other particulates in the air get attracted to the plates. The plates are then cleaned off, usually about once per week.

While they are no miracle cure, these devices do work as advertised. They do reduce the amount of dust, smoke and other small particles in the air, sometimes substantially. One key to their effectiveness is getting one the appropriate size for your room. A 10 x 15 foot room is on the outer edge of size for a moderate or small purifier. Any room larger will require a full-sized air home purifier.

One important addition to many quality home air purifiers is a HEPA filter. High Energy Particulate Air filters do more than attach particles to plates electrically where careless handling can actually put the particles back into the air. HEPA filters are specially designed to actually trap particles permanently.

Some are washable, others are not. Some are designed to last the lifetime of the device (usually 3-10 years), others will have to be replaced after 1-2 years or so. Prices vary considerably and the higher-priced models don’t necessarily have lifetime HEPA filters.

Noise is another important factor in judging a home air purifier. Some crackle and pop as a result of the electrical activity. Others have fans that can be heard easily above the computer in the home office. Good ones are so quiet you’ll barely notice them.

A good filter in a home air condition/heating unit is a must to keep dust and other particles reduced. But a home air purifier unit allows for a higher level of air cleaning, concentrated in an area like the bedroom or home office. If you spend large amounts of time there – and who doesn’t? – they can help reduce certain allergens.

Do Air Purifiers reduce Allergies?

One effective way to manage allergy symptoms is to reduce the amount of allergens present. For those who suffer from allergies caused by airborne allergens, a home or car air purifier can help do just that.

There are many different types on the market, though, some more effective than others.

Many home air purifiers produce ozone. Ozone is just an oxygen molecule (two oxygen atoms bonded together) with an extra oxygen atom alongside. Since the oxygen molecule is fairly stable, the third atom tends to get knocked off easily. When that happens it becomes what is called a free radical, and it is electrically charged.

Those charged oxygen atoms can harm the lungs. They carry energy and, because it is oxygen, readily participate in lots of biochemical reactions. Those reactions aren’t always beneficial. In extreme cases, they can increase the odds of lung and skin cancer. For some, asthma symptoms can be worsened by exposure to large amounts of ozone.

But the amounts produced by the average home air purifier are much lower than these dangerous levels. At most, some truly sensitive people can smell a hint of ozone in the air. The purpose of the ozone is to combine with potentially harmful particulates in the air and then move them to the walls or back to the air purifier.

Many good home air purifiers do their good work by creating a low intensity electric charge on metal plates. The purifier then uses a fan to move air around and the dust, animal dander and other particulates in the air get attracted to the plates. The plates are then cleaned off, usually about once per week.

While they are no miracle cure, these devices do work as advertised. They do reduce the amount of dust, smoke and other small particles in the air, sometimes substantially. One key to their effectiveness is getting one the appropriate size for your room. A 10 x 15 foot room is on the outer edge of size for a moderate or small purifier. Any room larger will require a full-sized air home purifier.

One important addition to many quality home air purifiers is a HEPA filter. High Energy Particulate Air filters do more than attach particles to plates electrically where careless handling can actually put the particles back into the air. HEPA filters are specially designed to actually trap particles permanently.

Some are washable, others are not. Some are designed to last the lifetime of the device (usually 3-10 years), others will have to be replaced after 1-2 years or so. Prices vary considerably and the higher-priced models don’t necessarily have lifetime HEPA filters.

Noise is another important factor in judging a home air purifier. Some crackle and pop as a result of the electrical activity. Others have fans that can be heard easily above the computer in the home office. Good ones are so quiet you’ll barely notice them.

A good filter in a home air condition/heating unit is a must to keep dust and other particles reduced. But a home air purifier unit allows for a higher level of air cleaning, concentrated in an area like the bedroom or home office. If you spend large amounts of time there – and who doesn’t? – they can help reduce certain allergens.

The Different Types of Food Allergies

According to data from the Mayo Clinic, about 2% of adults and 6% of children have some type of food allergy. Those percentages may seem low, but in a population of over 300 million in the U.S. that translates to 6 million and 18 million individuals, respectively.

Like any other allergy, a food allergy occurs when the immune system overreacts to an allergen. In this case, the allergens are typically milk, eggs, peanuts, shellfish and a few other foods.

In response to contact or ingestion, the body releases an antibody called IgE (immunoglobulin E) since it sees the food not as nutrition, but a foreign invader. The antibodies stimulate the release of histamine, prostaglandins and other compounds that produce the symptoms.

Food allergy symptoms tend to be more extensive than those that mark other allergic reactions. Nasal congestion and watery eyes are possible. But they are more often accompanied or overwhelmed by hives (itchy red welts that form on the skin), swelling of the lips, tongue or throat, wheezing and even nausea and abdominal pain.

In severe cases anaphylactic shock can occur. Anaphylaxis is a systemic (overall body) allergic reaction. It involves drastically lowered blood pressure, constricted airways leading to breathing difficulty, dizziness and other serious symptoms. It comes on quickly and, left untreated, sometimes causes death, as many as 200 per year in the U.S.

In some cases, food allergy reactions are localized. Fresh fruits and vegetables cause some to experience tingling in the mouth. The cause is thought to be proteins similar to those found in ragweed pollen.

Differentiating between a food intolerance and a food allergy requires a professional diagnosis by an allergist.

A skin prick test can frequently determine whether or not a person actually has an allergy to certain foods. The doctor takes an extract of the suspect substance and exposes the patient by inserting a small amount under the skin with a lancet. The skin is observed for about half an hour to note any swelling or itching in reaction to the extract.

A blood test may be warranted. This measures the amount of IgE produced in response to consuming the suspect food. But it is not always definitive.

Lactose intolerance, for example, is caused by the genetically induced lack of the digestive enzyme needed to safely process cow’s milk. The symptoms may be similar, but this is not an allergy.

Eliminating the troublesome food from the diet and environment is the first and best line of defense. Those with an allergy to eggs simply shouldn’t consume eggs or egg products. Those sensitive to peanuts and peanut dust can generally avoid coming into contact with it.

Since there is no cure yet for food allergies, avoidance is the best medicine. However, symptom relief is possible when accidents occur. Antihistamines are advisable. It’s also good to have on hand an EpiPen or similar device that allows allergy sufferers to inject a small amount of ephinephrine during an emergency. This can stave off any serious attack of anaphylaxis.