Although some substances are not harmful, some people may experience extreme reactions when they come in contact with them. When these substances, called allergens, come into contact with our immune system, the body produces an excessive amount of antibody protection substance against that substance, even though they are not harmful. This condition is called an allergy.
People with an allergic body are also called atopic. As soon as our immune system comes in contact with the allergen substance, it shows an excessive reaction and stores it in its memory. The next time it encounters this substance, it shows hypersensitivity by immediately producing a protective substance because it has previously impacted it.