Table of Contents
- Allergy facts
- Allergy overview
- What is an allergy?
- What is an allergy? (Continued)
- What causes allergies?
- What causes allergies? (Continued)
- Who is at risk for allergies and why?
- What are common allergic conditions, and what are allergy symptoms and signs?
- Allergic rhinitis (hay fever)
- Allergic eyes (conjunctivitis)
- Eczema (atopic dermatitis)
- Hives (urticaria)
- Where are allergens?
- In the Air We Breathe
- In What We Ingest
- Touching Our Skin
- Injected Into Our Body
Quick GuideAllergy: What Happens in a Nasal Allergy Attack
What causes allergies?
A common scenario can help explain how allergies develop. A few months after the new cat arrives in the house, dad begins to have itchy eyes and episodes of sneezing. One of the three children develops coughing and wheezing. The mom and the other two children experience no reaction whatsoever despite the presence of the cat. How can this occur?
The immune system is the body's organized defense mechanism against foreign invaders, particularly infections. Its job is to recognize and react to these foreign substances, which are called antigens. Antigens often lead to an immune response through the production of antibodies, which are protective proteins that are specifically targeted against particular antigens. These antibodies, or immunoglobulins (IgG, IgM, and IgA), are protective and help destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it. The allergic person however, develops a specific type of antibody called immunoglobulin E, or IgE, in response to certain normally harmless foreign substances, such as cat dander. Other antigens, such as bacteria, do not lead to production of IgE, and therefore do not cause allergic reactions. Once IgE is formed, it can recognize the antigen, such as cat dander, and can then trigger an allergic response. IgE was discovered and named in 1967 by Kimishige and Teriko Ishizaka. Continue Reading
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Medically Reviewed By: Ellen Reich, MD, Board Certified in Allergy and Immunology, Board Certified in Pediatrics and Michael Manning, MD, of the American Board of Allergy and Immunology.
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