For years, Barbara Rosvold dreaded the coming of fall. While many people rejoiced at the end of the hot, muggy Maryland summer, Ms. Rosvold, 51, of Middletown, MD, cringed, for she knew that with the autumn colors came ragweed pollen–and the accompanying stuffy nose, itchy eyes and congestion of seasonal allergies. Even taking medication didn’t help; although it eliminated the allergic symptoms, it left her tired and fuzzyheaded, a condition nearly as bad as the sneezing and stuffiness.
Ms. Rosvold is just one of an estimated 35 to 50 million Americans (1)–20 percent of the population–who suffer from seasonal allergic rhinitis or seasonal allergies. Overall, as many as 60 million Americans, or one in every five adults and children, have some form of allergy, which is the sixth leading chronic disease in the country. (1) The disease is far from just a minor inconvenience. Allergic rhinitis cost the United States $3.4 billion in 1993, of which $2.3 billion represents medications and $1.1 billion physician billing. Allergic rhinitis is gender neutral, affecting women at the same rate as men. (2) It’s also species neutral: even dogs get allergies!
One worrisome trend is that the incidence of allergies and asthma–a complication of allergies–appears to be on the rise. Increased airborne pollutants, rising levels of indoor allergens due to better and tighter construction methods, poor ventilation (3) and even a growing insistence to be “too clean,” the so-called hygiene hypothesis, are all possible causes. The hygiene theory holds that the infections you’re exposed to as a child help your immune system “learn” how to behave; too little exposure, and it goes overboard when it encounters anything foreign, even normally harmless antigens, says Dean D. Metcalfe, MD, chief of the Laboratory of Allergic Diseases at the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health, Bethesda, MD.

What’s An Allergy?

An allergy is a reaction of your immune system–your body’s defense against invading agents such as bacteria and viruses–to normally harmless substances that don’t cause problems for most people. These substances, which include pet dander, certain foods, molds and pollens, cause a false alarm reaction because your immune system treats them as invaders, generating large amounts of the disease-fighting protein immunoglobulin E, or IgE, a type of antibody. (2)

If you’re allergy-prone, the first time you’re exposed to an allergen, you begin to make large amounts of the corresponding IgE antibody. These IgE molecules attach to the surfaces of mast cells (in tissue) or basophils (in circulation). Mast cells are particularly plentiful in the lungs, skin, tongue and lining of the nose and intestinal tract, places where the outside of your body meets the inside, notes Dr. Metcalfe. “This activates the mast cells, and they spit out chemicals (including histamine, cytokines and leukotrienes) that go out into your tissues and cause the allergic response,” he explains. That’s the wheezing, sneezing, runny eyes and itching that are the hallmarks of allergies.

Blame Your Genes

Allergies can develop at any age, although heredity plays a key role in who develops them, (1) with genetic studies finding that 25 to 50 percent of children who have one allergic parent develop allergic rhinitis, asthma or both. While we don’t “grow out” of allergies, they may decrease or go into temporary remission. (4)

But additional causes are under investigation. One study found that the age at which your mother began menstruating could affect whether or nor you have allergies. Researchers theorize that differences in a woman’s estrogen levels–which play a role in the start of menstruation–somehow “programs” the fetus’ immune system. (5) Another study found a correlation between complications during pregnancy (hemorrhage, preterm contractions, restricted growth of the uterus and insufficient placenta), the development of a child’s immune and respiratory systems and an increased risk of asthma and allergic disorders. (6)

But a genetic predisposition is just part of the equation. You also need an environmental trigger–the allergen itself. Together, the two react like a lighted match on gasoline. For instance, says Dr. Metcalfe, you might be genetically predisposed to a birch pollen allergy. But, if you live in the Arizona desert, you’ll never be exposed to birch pollen. Move to Scandinavia, however, and you may want to invest in a truckload of tissues.

Allergies as You Age

Marsha Shapiro, 35, grew up on the coast of Virginia and never suffered from allergies until she moved to Atlanta, GA, at age 22. During her first four falls and springs in the southern city, she experienced numerous sinus infections. Finally, her health care professional recognized a pattern. “You’re allergic,” he told her, and prescribed a steroidal nose spray and a prescription antihistamine. The sinus infections disappeared.