TRIGGERS OF ALLERGY

In theory, just about anything that’s inhaled, swallowed, injected or touched could be an allergen to someone.  In reality, most allergic reactions are caused by a fairly limited number of well-known substances.

Allergies to inhaled substances are the most common.  We inhale 10-12 cubic meters of air each day, and (depending on the season and location) each cubic meter can contain hundreds of pollen grains and tens of thousands of mold spores.  Trees, grasses and weeds are the major sources of pollen.  A single ragweed plant may release a million pollen grains in a day, grains are so light in weight that they can travel in the wind for as much as 400 miles.

Molds grow throughout the world, both indoors and out.  Although molds are usually associated with damp areas, some indoor varieties can grow on surfaces where the moisture is as low as 15 percent.

Other important airborne allergens are animal dander, especially from cats and dogs; debris from dust mites and cockroaches; and house dust, which can contain all of these allergens and more.

Many myths surround food allergy.  About 40 percent of adults say that they have an allergy to one or more foods, but the correct figure is about .1 to 5 percent, depending on the age group.  Food allergies are more common in children, but most youngsters outgrow their food allergies by the age of 3.  Many people have avoided certain foods throughout their lives, not realizing that they probably haven’t been allergic to those foods since they were toddlers.

Other factors can contribute to a mistaken diagnosis of food allergy.  Coincidence may play a role.  A person who suffers nausea and diarrhea after eating a particular food might actually have a stomach flu or some other infection.  Spoiled or contaminated foods might cause symptoms blamed on allergy.

In addition, some people have enzyme deficiencies which prevent them from properly digesting certain foods.

Almost any food can trigger allergy, but the most common are nuts, eggs, milk, seafood and peanuts (peanuts are legumes, not nuts).  Unfortunately, seafood and peanut allergies don’t go away and may become more severe.

For some people, it appears that two or more factors must combine to produce allergy symptoms.  In recent years, several patients have been found who suffer anaphylaxis if they eat certain foods – celery, for example – and then engage in strenuous exercise.  Neither the food alone nor the exercise alone will cause the same problem for these individuals.

While folklore claims that chocolate is one of the most common allergens, only a few cases of true chocolate allergy have been reported.  Ranking with chocolate as a rare allergen: strawberries.

Injected allergens may include the venom of stinging insects such as honeybees, wasps, hornets, yellow jackets and fire ants; antibiotics such as penicillin, certain vaccines, antitoxins made with horse serum, and human blood products.  Injected allergens aren’t encountered very often, but they have the greatest potential for causing systemic anaphylaxis in sensitized individuals.

Ingredients found in cosmetics, perfumes and dyes are common skin sensitizing agents.  Latex gloves cause problems for some people, particularly those in the health care industry.  Saliva from an affectionate pet can be an allergen.  Poison ivy and poison oak may cause contact rashes.  Antibodies applied to the skin may also cause an allergic reaction.