Allergies cause the body to have a physical response to substances known as allergens. When this response occurs, the immune system is overreacting to a substance that does not cause any reaction at all in most people.
Many different substances cause allergic reactions.
Some are toxic, such as exhaust fumes, and others are non-toxic, like pollen and food. The most common allergens include Pollen from trees, grasses and weeds Dust mite particles Cockroaches Tobacco smoke, paint fumes, gasoline fumes, etc. The rarest type of allergic reaction is called anaphylactic shock. This is a severe reaction that can affect many organs at once. Symptoms include rapid decrease in blood pressure, rash or hives, difficulty breathing, abdominal pain, swollen tongue or throat, diarrhea, fainting and sometimes death.