“It’s fairly common,” says Dr. Davis. “I’ve even had 85-year-olds walk into my office with allergic rhinitis or hay fever. It’s unusual, but I’ve seen it.” Most people who develop adult-onset allergies usually do so in their twenties and thirties, though it’s possible to develop them at any age, Davis says. Allergic reactions happen when the body comes into contact with a specific substance, such as a food or an airborne particle, that it mistakenly identifies as harmful. Your body then produces antibodies called immunoglobulin E, or IgE, that attach themselves to certain cells, causing the cells to release a chemical called histamine. The histamine in turn causes inflammation, producing classic seasonal allergy symptoms, like red, watery eyes, and itching. Severe reactions to environmental and food allergies can cause a drop in blood pressure, and anaphylactic shock may occur. “Immunoglobulin E fights off infections,” Davis says. “It’s a good thing to have. But in about one in five people, too much IgE is misdirected against an allergen rather than something harmful. The body just makes a mistake.”
Unraveling the Adult Allergy Mystery
Researchers don’t know exactly what causes the body to react to an allergen after many years of uneventful contact with it. Many times, Davis says, something in the patient’s environment has changed that causes them to be exposed to a substance that they did not previously come into contact with very often. “Say someone has a tendency toward allergies; for example, a person might get married and their spouse has cats,” Davis says. “Cat dander is a very, very strong allergen. If you’ve never had indoor exposure to cats, it’s very possible for you to develop an allergy to them.” Another example is moving to a new state, where more allergens like ragweed and cedar pollen may be present in the air, and suddenly you develop seasonal allergy symptoms. One theory scientists have about allergy causes is called the “hygiene hypothesis,” which suggests that the highly clean environments of most Westerners can cause their immune systems to overreact to harmless things like pet dander and peanuts. However, there is not enough scientific evidence in existence yet to use this theory as a basis for prevention or treatment of allergies.
When to Consider an Allergy Test
If you suspect that you have developed seasonal or food allergies in adulthood, consult your family doctor or an allergist while you avoid the substances or foods you suspect. There are many allergy tests available to confirm a diagnosis, such as a blood test to check for the presence of specific forms of IgE. Another type of diagnostic tool is skin testing, in which a small amount of an allergen is applied to your skin to check for a reaction. In the case of suspected food allergies, you might try an elimination diet, in which you eliminate certain foods from your diet and then slowly reintroduce them, one at a time, to see if a reaction occurs, but make sure you talk with your doctor first. If an allergy diagnosis is confirmed, many therapies are available to eliminate or reduce symptoms. People with severe food allergies generally must avoid the foods in question and carry injectable epinephrine in case of accidental exposure. People with seasonal or other allergies can use a variety of medications, such as antihistamines and decongestants, to relieve seasonal allergy symptoms, and in some cases may respond well to allergy shots, which increase a person’s tolerance to certain allergens. Your doctor can help you determine the best course of treatment for your specific case.
