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What Are Allergies?

Why I Have Allergies, Why They Make Me Sick, and What I Can Do About Them


Why do I have allergies? Can I develop allergies?

As a retired Registered Nurse, I'm often asked questions just like this about allergy information. People want to know what makes them different from their friends who can enjoy the outdoors, pet their cats, and dust their house without a sniffle.

Allergies tend to be genetic, running in families. Interestingly though, family members are not always allergic to the same things. Their allergies may not always affect them the same way. Dad may be allergic to almost all the pollens, sister allergic to several foods, grasses and animals, and little brother allergic to mold and ragweed. Mom and big brother may have no allergies at all. One family member may have hives or skin allergies, another asthma, and another hay fever. Or they may have any combination of these three.


"A family history of allergies is the single most important factor that predisposes a person to develop allergic disease. If one parent has allergic disease, the estimated risk of the child to develop allergies is 48%; the child's risk grows to 70% if both parents have allergies."


Exposure to new allergens can also bring on allergic symptoms. It's very common for me to hear people say, "I didn't have any allergies at all until I moved here." They may be referring to a move from another area of the country where there are different pollens present, or just a move across town, perhaps to a home with different environmental allergens present. Either way, these people probably already had a genetic tendency toward allergies, often called "atopy" or being "atopic" by those in the medical field. Sometimes atopy is associated with an "allergic triad", which is:

  1. Asthma
  2. Dermatitis (Allergic Skin Conditions)
  3. Rhinitis (Hay Fever)

What this means is that the person who has this genetic tendency toward hypersensitivity is more likely to develop asthma, allergic skin conditions, or allergic rhinitis. There seems to be an association between these three diseases. The person who experiences one of them is more likely to suffer from one or both of the others at some time in their life. Atopic people are more susceptible to developing an overreactive immune system. The immune system is the part of our body that fights bacteria, viruses, and anything else it recognizes as foreign. But it becomes hypersensitive when it begins to see normal substances as intruders.


Why do allergies make me sick?

Our bodies are a fascinating handiwork. We are created in such a way that every part coordinates in minute precision with every other part.


For example, on the surfaces of some cells there are tiny areas that require powerful microscopes to explore. These areas are receptors for antibodies. As you might know, antibodies are cells that ward off infection, viruses, and other threats. Antibodies are highly specialized. Each has it's own specific assignment. Some are responsible to fight a certain virus, others to fight a specific bacteria. Antibodies are also called immunoglobulins. Immunoglobulin E (IgE) is the antibody commonly associated with allergies.

"Each type of IgE has specific 'radar' for one type of allergen only. That's why some people are only allergic to cat dander (they only have the IgE antibodies specific to cat dander) and others seem to be allergic to everything (they have many more types of IgE antibodies.)"
-- From

Receptor cells for IgE are located in various parts of the body, including areas near the eyes, ears, sinuses, throat, lungs, skin, and gastrointestinal tract. These receptor cells are called mast cells. Other cells with receptors for IgE are in the blood stream. They are called basophils. A few other cells have receptors for IgE also, but mast cells and basophils are the most prominent ones.

The problem for allergy sufferers occurs when the body becomes confused about substances such as pollendust mitescat dander, common molds, foods or medications. Each of these substances can be recognized as an intruder, and the body begins creating IgE antibodies toward it. But it is not usually able to get the mature IgE in place soon enough to do much damage in the first round.

However, the body has a fantastic memory! It never forgets that challenge to it's integrity. The next time the immune system is exposed to that allergy information or allergen, such as cat dander, it rapidly produces IgE cat dander antibodies. As these IgE antibodies are produced, a complicated chain of microscopic events takes place within just a few minutes. This results in presentation of the IgE antibody to the mast cells in the tissues surrounding the eyes, sinuses, nose, and lungs, and to basophils in the blood stream. The receptors on mast cells have a high affinity or liking for IgE antibodies. The union of IgE antibodies with mast cells enables the allergen to cross-link between two of the antibodies. As allergens begin to rapidly cross-link with more IgE on the receptor sites of the mast cell, the mast cell releases powerful chemicals such as histamines and leukotrienes, both of which mediate (or bring on) inflammation.

Inflammation is not always bad. Inflammation causes the blood vessels in the skin to dilate, allowing blood to rush in, bringing antibodies to fight the infection or intruder. As the blood rushes to the area, fluid containing antibodies is leaked into the surrounding tissues from the blood, and the tissues become swollen. Antibodies in this swollen area are working hard to fight infection.

But for the allergy sufferer, this inflammatory process is not needed, because there is no real intruder to fight. The inflammation in the allergic response releases chemicals that can cause itching in the eyes and skin and congestion in the sinuses and lungs. This results in swelling and increased mucous production which can obstruct breathing and cause a runny nose and itchy, watery eyes. In some cases hives may occur as fluid seeps into the outer layers of skin. Each time the allergy sufferer is exposed to the allergen, another series of these microscopic processes occurs. As long as there is exposure to the allergen, there seems to be no end to the inflammatory response.

It's also important to note that hours after recovery from the initial allergic reaction, a second or late phase reaction may occur. In the late phase, the receptor cells in the blood (basophils) influence other blood cells called eosinophils to release more mediators of inflammation. Enzymes are released during this late phase, some of which can cause permanent tissue damage if allowed to continue over time. This is especially serious for asthmatics because it can lead to what doctors call "airway remodeling." The lungs are remodeled by replacing healthy tissue with scar tissue. For additional information on this late phase response, see the section titled "Early and late phase reactions" on the following page: You may also be interested in viewing the video included in that section.


"Eosinophils also play prominent roles in late-phase reactions that affect some people with allergies and asthma, particularly with symptoms of nasal congestion that can occur hours after an initial episode of allergic rhinitis. If you have uncontrolled asthma, constant eosinophil activity may lead to airway remodeling - the replacement of healthy tissue with scar tissue - and can potentially cause irreversible loss of lung function.
aa4dummiesPreventing this type of serious lung damage is one of the main goals of treating asthma early and aggressively..."

-- From Allergies and Asthma For Dummies by William E. Berger, M.D.


The First Line of Defense: Avoidance

The first recommendation I always make to people is to avoid the allergens to which they are allergic. If you can totally avoid the things you are allergic to, then you can eliminate all remaining action steps. Unfortunately, it is almost impossible to totally avoid allergens since they are a prominent part of our environment. But we can take some very helpful steps to prevent exposure to many of them.

For example, when people tell me they wake up with allergy symptoms, allergy testing often shows that it's because they have been breathing in dust mite allergen all night! I can help them eliminate a lot of their problem by recommending they purchase mite-proof mattress, box spring and pillow covers. Dust mites feed on our dead skin cells that slough off in our mattresses and pillows. By simply covering our beds and pillows with mite-proof encasings, we will be helping prevent allergies by putting up a major barrier that dust mite allergen can't penetrate. Even for those without dust mite allergies, mite-proof covers can also protect against cat dander, mold, or other allergens that settle in our mattresses and pillows.

Our climate is very humid during these summer months, so I also recommend a dehumidifier for patients with environmental or mold allergies. By reducing the humidity in our homes to around 50%, we can make it difficult for mold and dust mites to survive. Don't forget to have your air ducts checked by a professional air cleaning service also. Mold growth or buildup of pet dander and other allergens in the furnace and ducts can keep allergens continually circulating in your home. Be sure to select a good quality furnace filter also. A furnace filter designed to remove pet hair, mold, smoke particles, bacteria, and viruses can go a long way toward making the air you breathe cleaner.

Other measures I recommend to prevent allergies include laundering all bedding in hot, soapy water (or adding a cold-water mite killing agent); using HEPA air cleanersdusting frequently; using easy to clean window treatments; and weekly vacuuming (be sure your vacuum has a good HEPA filter also). If you're allergic to pollens, avoidance is a little harder. Just walk outside your door and you're exposed. But simple measures such as wearing a Latex-Free Mask when mowing the lawn or gardening, and keeping the windows closed in your home and car can help.

For those with mild allergies, this first line of defense may be enough. But often medication must be added to the treatment plan.

The Second Line of Defense: Medications

Antihistamines and leukotriene modifiers (sometimes called antileukotrienes) block the histamine and leukotrienes that are released when antibodies unite with mast cells. Allergy products like Antihistamines are used for some allergic skin reactions such as hives, as well as respiratory allergies such as hayfever and are available as prescriptions and over the counter. If you are going to have a skin test for allergies, be sure to stop taking any type of antihistamine a few days prior to the test. If present in your system, they could block the reaction in the skin so the test would appear to show no allergies when in fact you might have some (also called a false negative). Allergy products like Leukotriene modifiers are used to treat allergic hayfever and asthma. They may also be helpful in treating angioedema (generalized swelling which can cut off the airways). Since it is the release of histamine that causes the positive reaction in skin testing, leukotriene modifiers usually do not need to be stopped prior to skin testing. Read product labeling carefully as some antihistamines can cause drowsiness and should not be taken when driving or operating machinery. Leukotriene modifiers usually have minimal or no side-effects.

Oral decongestants help to reduce congestion and stuffiness in the sinuses. People with high blood pressure should not take these decongestants because they can elevate blood pressure. They can also cause some people to feel jittery. Occasionally they may cause a rapid heartbeat, and if this occurs you should stop taking the decongestant and consult your physician. Over the counter nasal decongestant sprays are not as likely to cause side effects as oral decongestants because less is absorbed. However, if you experience dizziness or a rapid heart beat while using over-the-counter nasal sprays, you should stop them immediately and check with your physician. Prolonged use of over-the-counter nasal decongestant sprays can cause a rebound effect in which the spray itself initiates the congestion. This results in increased symptoms and dependency on the spray to overcome the rebound effect it causes. Never use over-the-counter nasal decongestant sprays for more than a few days without your doctor's advice.

Prescription-strength nasal steroid sprays and a nasal antihistamine spray are also available. These help reduce the inflammation caused by the allergic response. At recommended doses, nasal steroid sprays are usually considered safe for even long-term use, since only very minute amounts are absorbed systemically. They usually don't cause the side effects of oral decongestants. Never use more than the prescribed dose of these sprays - usually one to two sprays in each nostril once a day. To minimize systemic absorption, always use the lowest prescribed dose that works for you. If one spray works, don't use two! Many doctors recommend saline nasal irrigation to help moisten and cleanse the nose and lower sinuses.

Asthma is often associated with allergies, and asthma attacks can be triggered by airborne allergens. Asthma medications are usually one of two types, a long-term control medication or a quick-relief or "rescue" medication. Orally inhaled steroids, which reduce inflammation, are an example of a long-term asthma medication. Many physicians recommend them as a baseline treatment for asthmatic patients. Bronchodilators are often prescribed to relax smooth muscles in the airways. They may be used as long-term medications, but often they are used as quick-relief rescue medications. They can sometimes cause the heart to beat irregularly or too fast.

Cromolyn sodium prepares the mast cell to prevent the release of histamine and leukotrienes. It is sometimes recommended to help prevent allergies prior to exposure. Cromolyn sodium should not be used to treat an allergic attack. To be effective, it must be used several days or weeks prior to exposure to the allergen. Cromolyn sodium is considered safe when used as directed. However if you experience any unusual symptoms while using it, you should stop it immediately and check with your physician.

There are other treatments and medications that are sometimes prescribed. Always follow your doctor's recommendations carefully and share with your physician any questions or concerns you may have.

The Third Line of Defense: Allergy Injections

Also known as allergy shots, these are small doses of the actual allergen to which you are allergic that are injected into the skin. The study of how allergy injections work is very interesting. It is also a bit confusing, because there is still much research going on in this area. It might be helpful to review Part 1 of this series for a detailed explanation of allergic response as a refresher prior to reading this next section.

One widely accepted theory is that, for reasons yet unknown, when allergens are injected into the skin rather than inhaled as normal, the body doesn't recognize the offending allergen in the same way. Instead of developing IgE antibodies as usual, the body begins developing IgG antibodies toward the allergens. It is thought that these IgG antibodies actually block the IgE antibodies from uniting with the receptor sites on mast cells. If you recall from Part 1 of this series, it is the union of IgE antibodies and mast cells that initiates allergy symptoms. It is also thought that eventually allergy injections may result in a decrease in IgE, though it is not known for sure how this works.

The goal of allergy injections (also known as immunotherapy) is to be able to reduce or eliminate the need for medications, and after several years even the shots themselves. Many people find they can be exposed to moderate amounts of the offending allergen with less or no symptoms after they have been on allergy shots for awhile. For example, they may be able to mow the lawn or pet their cat without a major allergy attack. However, some people do find that at least some of their symptoms eventually return after shots are discontinued. Always talk with your doctor before changing your medication regimen or stopping your injections. This is especially important if you have asthma.



"Three basic therapeutic techniques should be considered in treating either seasonal or perennial allergic rhinitis:

  1. avoidance of the offending allergens
  2. use of appropriate drugs
  3. immunotherapy (injection treatments to effect hyposensitization or desensitization)

When feasible, avoidance is the preferred form of treatment, since it both relieves symptoms and eradicates the cause of the difficulty."
JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION Nov. 27 1987-Vol. 258, No. 20, Pp. 2854, 2855; M. Kaliner, MD, P. Eggleston, MD and K. Mathews, MD

For many people, a combination of avoidance, medications, and allergy injections are needed to control their symptoms in the beginning. Once under control, some patients have been able to gradually eliminate medications through the supervision of their physician. Eventually some patients are able to stop allergy shots with only minimal symptom return. Even then, we still recommend they use environmental control measures when possible to provide optimal symptom control and less exposure to the allergen. Less exposure means less challenge to the immune system, thus it may mean less chance that the allergy symptoms will return when shots are discontinued. You should always talk with your physician about which approaches are best for you.

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