Boston , MA — Many of us welcome the warm weather as a chance to get out­doors after winter’s confinement. But for people with hay fever, outside can be the worst place to be in the spring. The April issue of Harvard Women’s Health Watch reports why certain people get allergies, what you can do to prevent allergic reactions, and what medications you can take to treat them.

Various Allergies

Hay fever, or seasonal allergic rhinitis, is an immune response provoked by airborne sub­stances, mostly plant pollens and mold spores. The symptoms — sneezing, runny nose, itchy eyes, stuffy sinuses, and tickling throats — aren’t life-threatening, but they can make you miserable. The Harvard Women’s Health Watch reports that the most effective medications for hay fever are anti-inflammatory nasal sprays, also called nasal corticosteroids.

Allergic rhinitis isn’t just a seasonal prob­lem. Perennial allergic rhinitis, which occurs year-round, is triggered by common household allergens such as dust mites, animal dander, and mold.

You develop an allergy when your immune system becomes hypersensitive to a normally harmless substance, such as inhaled pollen or dust mite particles. Once sensitized, the immune system overreacts every time it’s exposed.

Allergies not a problem for some

Not everyone has allergies. Some people are genetically predisposed (one or both parents have allergies), while others may de­velop allergies in response to the environ­ment. One theory, called the “hygiene hypothesis,” holds that lack of early exposure to dirt, dust, and certain childhood infections makes the immune system hypersensitive later on. On the other hand, the Harvard Women’s Health Watch explains, repeated exposure to certain allergens, such as dust mites, may further predispose the offspring of allergic parents to develop allergies.

Also in this issue:

Insights from a breast cancer surgeon who got breast cancer herself Weighing the alternatives to COX-2 drugs A doctor answers: What causes tingling hands at night? Is the ultra-low dose estrogen patch available?