People can develop allergies at all different ages.
Almost anything that can be inhaled, swallowed , injected or touched can cause an allergic reaction for someone. The most common allergens are pollens, molds, house dust mites, animal dander, foods, stinging insects, and medications. It makes antibodies against the allergen. When the body sees that same substance again, the antibodies unleash their attack on it. The result is a release of a variety of chemicals, such as histamine, amongst others.