Animal allergies cause runny noses, sneezing and itchy, watery eyes in children as well as adults. Contrary to popular belief, it is not animal hair or fur that triggers most reactions. Rather, it is proteins found in dander that flake off the animal’s body and find their way into the air. Proteins in dried animal saliva, urine and blood are also major allergens for some people.

Animal allergies occur when the body’s immune system overreacts to one of these normally harmless substances. The substance enters the body and the immune system responds by producing a specific type of antibody called immunoglobulin E (IgE) to combat the allergen. This process, known as sensitization, does not usually trigger allergy symptoms at first. However, subsequent exposure to the allergen can trigger an allergic reaction.

Animal allergies can take two years or longer to develop, as a child is exposed to the allergen repeatedly and becomes sensitized to it. For this reason, it is often difficult to diagnose an animal allergy before buying a pet – only months or years with the animal will prove if an allergy is present.

Direct contact with an animal is not needed to develop an allergy. Flakes from dander, saliva and urine are extremely lightweight and easily become attached to larger particles, which can become airborne or stick to surfaces or objects. These particles remain in the environment for weeks or even months after an animal has departed. The allergens can also be transported from one environment to another on clothing or objects.