What is allergy?

What is allergy?
Allergies occur when the immune system becomes unusually sensitive and overreacts to common substances that are normally harmless, such as pollens, molds, dust or food. Genetic tendency plays a role since allergies tend to run in families. Allergy develops when exposure to certain substances leads to sensitivity. These substances that cause allergic reactions are called allergens.

The immune system produces various antibodies. The antibody that is involved in allergic reactions is called IgE. During an allergic reaction allergens come into contact with special cells called "mast cells" that are found in the lining of the nose, lungs, skin and intestinal tract. The IgE antibodies that are attached to these cells cause the release of many chemicals, including histamine, which results in inflammation and symptoms of allergy.

Depending on the individual and the particular allergen, allergy symptoms can occur in the upper and lower respiratory tracts, the skin, digestive system and other organs. Each individual is different. For example in the case of cat allergy, one person might have symptoms affecting the nose while another might have wheezing in the chest.

Some allergies develop after a long period of exposure while others often seem to develop after a relatively short exposure. Some are life-long while others may subside over time. Once sensitization occurs, avoidance of allergens is the best way to prevent symptoms.

Dust, Pet and Mold Allergies
Our multipage brochure about several common allergies.
Atopic Dermatitis - Eczema
by Dr. Liliane Gendreau-Reid, MD, FRCPC Pediatrics; FRCPC Clinical Immunology & Allergy; Clinical Assistant Professor of Pediatrics UBC, Victoria, BC
Eosinophilic Esophagitis
by Dr. Harold Kim, Allergist, Kitchener, Ontario
Cosmetic Allergies — Is Soap Really Good for You?The first of a series of articles designed to help AAIA members better understand cosmetic allergies. [read more...]
Allergic Rhinitis
by Dr. Harold Kim, Kitchener, Ontario
Learn the link:
Managing your asthma and your seasonal allergies. [read more...]
Rhinitis: The Facts
by Liliane Gendreau-Reid, MD, Victoria, BC
Airborne Allergens Avoidance Tips
by Liliane Gendreau-Reid, MD, Victoria, BC
Hives (Urticaria)
Hives are a common occurrence, affecting up to 25% of the population at least once in their lives. They can be short term, lasting only a few days to six weeks, but they can be chronic and last for months or years. [read more...]
Allergy Season — It can affect your thinking !!!
by George Luciuk, MD, FRCPC
Does Allergy Protect Against Cancer?
by Dr. Susan Waserman, MD, FRCP, Hamilton, Ontario
Drug Allergy: How You Can Help Your Allergist Make the Diagnosis
by Amin S. Kanani, MDCM, FRCPC
The Positive Side of Being Allergic
by Robin Bayley, Victoria, British Columbia
Are you allergic to cats?
from an article by Thomas A E Platts-Mills, Asthma and Allergic Diseases Center, University VA Medical Center, Charlottesville, VA
Scents in the Workplace
Individuals who are affected by allergic rhinitis and asthma may find that strong scents trigger their symptoms. [read more...]
The Hygiene Hypothesis
At the CSACI Annual Scientific Meeting held in Ottawa in October 2004, there was an interesting debate on the Hygiene Hypothesis by two experts in the field of allergy. These are some of the main arguments. Reported by Mary Allen. [read more...]
Tips to reduce mold exposure
Ten things you can do. [read more...]