The Mayo Clinic: Reasons for developing allergies later in life not always clear

DEAR MAYO CLINIC: I didn’t have allergies when I was younger. But now in my 40s, I seem to get allergy symptoms during the spring and summer. Is it possible to develop allergies as an adult? Should I get tested? If so, what do allergy tests involve?

ANSWER: You can develop allergies later in life, and there is definitely value in getting tested to see if your symptoms are linked to allergies. If they are, the test results will give you information about what you’re allergic to and help guide you as you decide on treatment. Allergy tests usually involve a skin test, a blood test or both.

Allergy development typically has two phases. During the first phase, called sensitization, you come in contact with a harmless substance and your body mistakenly starts making allergic antibodies, called IgE antibodies, to fight that substance. Those antibodies don’t do anything until you are exposed to the substance, or allergen, again. At that time, the second phase starts. The allergen binds to the IgE antibodies. That sets off a cascade of immune reactions in your body, such as itchy or watery eyes, nasal congestion and sneezing, among others.

Common triggers for seasonal allergies include tree and grass pollen, which are prevalent in the spring and summer; ragweed pollen or other weed pollen, which are common in the fall; and spores from molds and fungi, which tend to be widespread in warm-weather months. This is in contrast with the house dust mite allergen, which is considered perennial (present all year long) but has also shown seasonal variations based on ambient humidity.

It’s not always clear why some people develop allergies later in life. A common reason for developing new seasonal allergies is moving from one geographic region to another. If you grew up in an area that has certain plants and trees, then moved to another area that has a mix of vegetation you’ve never before been exposed to, you may develop allergies to those new plants.

If, as in your situation, allergy symptoms develop but you aren’t sure what you might be allergic to, or even if your symptoms really are allergies, it is worthwhile to go through allergy testing. The tests can show what you are sensitive to, and knowing that can go a long way toward customizing treatment.

A procedure called a skin prick test can be very helpful in diagnosing allergies. During the test, small amounts of material that can trigger allergies are pricked into the skin of your arm or upper back. Your doctor then watches for signs of an allergic reaction in those areas. If you’re allergic to a certain substance, you will develop a raised itchy bump at the test location on your skin.

In some cases, your doctor also may recommend a blood test to measure the presence of allergen-specific IgE. A blood sample is sent to a medical laboratory, where it’s tested for evidence of sensitivity to possible allergens.

A wide variety of effective treatments are available for seasonal allergies. Some allergy treatments, like certain antihistamines, nasal corticosteroid sprays, saline sprays and washes, are available without a prescription at most pharmacies. Other oral medications and some nasal corticosteroids require a prescription from your doctor.

To most effectively control your symptoms, talk to your doctor about getting tested for allergies. Then work with him or her to find the therapies that are best for your situation. — Rohit Divekar, allergic diseases, Mayo Clinic, Rochester, Minn.

The MAYO CLINIC Q&A is an educational resource and doesn’t replace regular medical care. Email questions to MayoClinicQ&A@mayo.edu. For more information, visit mayoclinic.org.