Allergies

When you walk into a new place and start sneezing or wheezing for no obvious reason, only to have the symptoms vanish when you leave — that is a classic allergic reaction. It happens because some people are sensitive to tiny particles in the environment, like pollen or dust mites, which differ from place to place.

Allergy is defined as the exaggerated response of the immune system to certain antigens present in the environment. The substances that trigger this response are called allergens. Unlike other immune responses that produce IgG or IgM antibodies, allergies involve the production of IgE-type antibodies.

Common examples of allergens include:

• Mites in household dust
• Pollens from plants
• Animal dander (tiny flakes of skin from pets)

The symptoms of an allergic reaction include sneezing, watery eyes, a running nose, and difficulty in breathing. These symptoms arise because allergens cause the release of chemicals like histamine and serotonin from mast cells in the body.

To determine the cause of a patient's allergy, doctors expose or inject very small doses of possible allergens into the patient and study the reaction. This is called allergy testing.

Treatment to quickly reduce symptoms involves drugs such as:

• Anti-histamines (which block histamine)
• Adrenalin (epinephrine)
• Steroids …