What Causes Allergies?

Allergic reactions are caused by substances known as allergens. These substances can be found in a variety of sources such as pollen, mold spores, dust, animal dander, and certain foods. These substances induce the hypersensitive state of allergy and stimulate the formation of reaginic antibodies, eading to the release of chemicals like histamine, which cause the symptoms associated with allergies, such as sneezing, itching, and swelling.

The immune system plays a crucial role in the development of allergies. It contains specialized white blood cells called lymphocytes, which include B cells and T cells. B cells are responsible for producing antibodies that target specific antigens, while T cells directly attack these antigens. In allergic reactions, the B cells produce antibodies that bind to allergens, leading to the release of histamine from mast cells. This release is what causes the visible symptoms of an allergic reaction, such as a runny nose or wheezing.

Genetics also plays a significant role in the likelihood of developing the severe form of allergies known as Type I allergies. These include hay fever, insect venom allergy, and asthma, and involve the class of antibodies known as immunoglobulin E (IgE). A particularly severe, often fatal, type I allergic reaction is known as anaphylaxis (which is especially common following insect stings). Some individuals have a genetic predisposition to type I allergic reactions. This tendency can run in families, although it is not linked to a single gene. People with this predisposition are often referred to as atopic (meaning “uncommon”), and make up about 10% of the population.