1. 'Tis the season – What are allergies?


They result from the immune system overreacting to foreign particles like pet dander, pollen, dust mites, and food proteins. An initial encounter prompts the body to produce antibodies against the particle, or allergen. When a person is exposed again, the allergen triggers the antibodies to bind mast cells, and they release other inflammatory agents such as histamine and leukotrienes, which cause the runny noses, coughing, and watery eyes, collectively known as allergic rhinitis. Most people just call it miserable.

2. Do allergies create other problems?

Asthma and eczema (or allergic dermatitis), to name just two. The extreme reactions, often after someone is stung by an insect or eats something made with peanuts, can induce anaphylaxis. When this happens, blood vessels dilate rapidly, causing precipitous, sometimes fatal drops in blood pressure. Atopy is the term used to describe all types of allergic reactions....

3. Besides the symptoms, what else can be treated?

People with allergies frequently take histamine and leukotriene blockers. Scientists want to find ways to control the signaling of dendritic cells, which notify the immune system when foreign particles invade the body. They're also looking at eosinophils, the white blood cells involved in the allergic inflammation and bronchoconstriction associated with asthma. The pathways guiding interactions between immunoglobulin E and its receptors also are under study.

4. Why are only some people affected?

Allergies are hereditary, but their exact genetic basis is still unclear. Researchers have identified atopic susceptibility loci on several chromosomes, including 2q33, 4q24-q27, and 5q31-q33 (the interleukin-4 gene cluster). Variations at some loci may increase susceptibility only if variations are present at other loci, making it difficult to sort out the real culprits.1

5. Is there any stock in the "hygiene hypothesis"?

Evidence regarding the hygiene hypothesis – that youngsters who live in germ-free environments may develop allergies and other illnesses later in life – is contradictory. Kids with cats are less likely to develop animal allergies, and hepatitis A infections may lower the risk of developing allergies. But mice with the flu are more likely to have asthma.2

- Maria W. Anderson

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