About This Condition
Allergies are responses mounted by the immune system to a particular food, inhalant (airborne substance), or chemical. In popular terminology, the terms “allergies” and “sensitivities” are often used to mean the same thing, although many sensitivities are not true allergies. The term “sensitivity” is general and may include true allergies, reactions that do not affect the immune system (and therefore are not technically allergies), and reactions for which the cause has yet to be determined.
Some non-allergic types of sensitivity are called intolerances and may be caused by toxins, enzyme inadequacies, drug-like chemical reactions, psychological associations, and other mechanisms.1 Examples of well-understood intolerances are lactose intolerance and phenylketonuria. Environmental sensitivity or intolerance are terms sometimes used for reactions to chemicals found either indoors or outdoors in food, water, medications, cosmetics, perfumes, textiles, building materials, and plastics. Detecting allergies and other sensitivities and then eliminating or reducing exposure to the sources is often a time-consuming and challenging task that is difficult to undertake without the assistance of an expert.
Common symptoms may include itchy, watery eyes; sneezing; headache; fatigue; postnasal drip; runny, stuffy, or itchy nose; sore throat; dark circles under the eyes; an itchy feeling in the mouth or throat; abdominal pain; diarrhea; and the appearance of an itchy, red skin rash. Life-threatening allergic reactions—most commonly to peanuts, nuts, shellfish, and some drugs—are uncommon. When they do occur, initial symptoms may include trouble breathing and difficulty swallowing.
People with allergies and sensitivities are typically advised to avoid exposure to particular allergens, such as tree and grass pollens, dust mites, molds, specific foods, latex, or environmental and household irritants. Those who have experienced severe reactions should wear a medical alert tag listing their allergens.