Allergen

A substance that is foreign to the body and, in some people, can cause an allergic reaction. An allergen is a substance that can cause an allergic reaction. Allergens are substances that, in some people, the immune system recognizes as “foreign” or...

Allergy

A hypersensitivity of the body’s immune system in response to exposure to specific substances (antigens). A hypersensitive immune reaction to a substance that normally is harmless or would not cause an immune response in most people. An allergic response may...

Amenorrhea

The failure of a woman to menstruate. Amenorrhea is the absence of a menstrual period. Primary amenorrhea is when a young woman has not yet had a period by age 16. Secondary amenorrhea describes someone who used to have a regular period but then it stopped for at...

Analgesic

A medicine used to reduce pain. Pain medications are also called analgesics. Analgesics include aspirin, acetaminophen, and ibuprofen. Every pain medicine has benefits and risks. Specific types of pain may respond better to one medication over another. Results also...