Why does allergy happen?

Allergies are your body's response to allergens, a clear sign that your immune system is in overdrive. The first time the body contacts with an allergen, plasma cells are stimulated by TH2 cells, which are a type of helper lymphocytes, and these lymphocytes attach to the surface of the cells. This process perpetuates the cells' reaction by having another encounter with the allergen.

When these cells are activated, they release a chemical known as histamine, as well as numerous other unruly substances involved in allergic reactions and inflammation. These elements cause the unwelcome symptoms of allergies by reacting with parts of the body. This reaction is the acute response, which typically occurs within five to ten minutes.

Allergies are an overreaction of the immune system (defense system of the body) to harmless substances. Different substances can trigger the immune system to respond. These substances are known as an allergen. When the immune system comes in contact with an allergen, it builds up the sensitivity to the substance. This helps the immune system to remember the allergen and begin to make antibodies against it. This process is known as sensitization.

It can take several days to build up the sensitization. If a person is exposed to the allergen, the immune system recognizes and remembers it. The antibodies formed to begin to attack the allergen and this results in the symptoms an affected person experiences. Symptoms may include irritation, inflammation, itching, runny nose, wheezing, difficulty breathing, and many more.