Lung Care : Asthma Center
What You Always Wanted to Know About Allergies, but Were Afraid to Ask
Topic of the Month
Mark Davis-Lorton, MD
Division of Allergy & Immunology
What is an allergy?
Dust mites and their waste
The job of the bodies immune system is to identify foreign substances (such as viruses and bacteria) and get rid of them. Normally, this response protects us from dangerous disease.
If you have allergies, you have a supersensitive immune system, which reacts to harmless substances, like plant pollen, dust mites, or animal dander. These substances are called allergens. Your immune system overreaction is what causes your allergy symptoms.
Who gets allergies?
Super sensitive immune systems tend to run in families. Although no one is born with allergies, you can inherit the tendency to develop them. One thing is true for all allergic people: the more often and the more directly you come in contact with an allergen, the more likely you are to develop an allergy to it.
Allergies usually begin to develop in childhood, although they can show up at any age. The most common allergies among infants are food allergy and eczema (patches of dry skin). In older children and adults, allergic rhinitis (hay fever) is more common. As some children get older their symptoms decrease, only to reappear later in life.
What causes allergy symptoms?
The most common kind of allergy involves a gradual build-up of proteins called IgE antibodies. For example, the first time you pet a cat, your body may overact and produce IgE antibodies in response to the animal's hair. The antibodies attach to mast cells in your nasal passages and remain in your body. Each time you get near a cat, your body will produce more cat hair IgE antibodies. At some point-in trying to protect you from this perfectly harmless cat hair -your mast cells will release molecules such as histamine and lipid mediators. These molecules cause your allergy symptoms such as sneezing, watery eyes, and a runny nose. Over time, cat hair has become an allergen for you.
Depending on your allergy, your symptoms may range from runny nose to itchy hives to a serious, lie-threatening reaction called
anaphylaxis. Anaphylaxis causes swelling of body tissues, vomiting, cramps, and a drastic drop in blood pressure. It occurs most often people who are allergic to insect stings, drugs, and certain foods.
Hair and saliva of animals with fur or feathers
Cockroaches and their waste
Weed, grass and tree pollens
Mold and mildew spores
Stinging insects such as bees, wasps and hornets
Drugs such as penicillin
Foods such as eggs, milk, nuts and seafood
Plants such as poison ivy and poison oak
Ingredients found in dyes, cosmetics, and latex
Types of allergic reactions
Allergic rhinitis is an inflammation of the mucus membranes in the nose, throat sinuses, and/or ear passages, which occurs when you inhale an allergen. Common symptoms include nasal stuffiness, sneezing, nasal itching, clear nasal discharge, and itching of your ears and/or roof of the mouth. Your symptoms may be season or year-round.
Red, itchy, watery eyes are typical of allergic conjunctivitis (eye allergy).
Symptoms of atopic dermatitis (eczema) include red, itchy, dry skin, usually on elbows, knees, and skin folds.
Uritcaria are itchy welts, which may appear on any part of your body.
Contact dermatitis is an itchy rash, which breaks out where an allergen has touched your skin. Poison ivy is one common culprit.