What causes allergies?

An allergy is a special immune reaction to a substance in the environment. When a child with allergies comes into contact with one of these substances, known as an allergen — either by touching it, breathing it, eating it, or having it injected — her body views it as a dangerous invader and releases histamines and other chemicals to fight it off. These chemicals irritate the body and cause symptoms such as a runny nose, sneezing, itching, and coughing.
Possible allergens include food, drugs, insects, animal dander, dust mites, mold, and pollen. Depending on the type of allergy, it can cause respiratory symptoms (allergic rhinitis), skin symptoms (like eczema), or intestinal problems (from food allergies, for example).

The most likely culprits of nasal allergies in babies are:

• Dust mites — microscopic organisms that thrive on human skin flakes (nearly 85 percent of allergy sufferers are allergic to dust mites)

• Animal dander — those white flaky specks (shedding skin and hair) on cats, dogs, and other furry animals

• Molds — fungi found in wet, damp places such as bathrooms and basements

Some children are allergic to down and feather pillows, or chenille or wool blankets. And while most experts don't think children can be allergic to tobacco smoke, it can certainly make their allergic symptoms worse.

A child will inherit the tendency to be allergic, but not necessarily the specific allergies. For example, if one of your child's biological parents has hay fever or pet allergies, there's a 50 percent chance your child have some sort of allergies as well. That probability jumps to 75 percent when both biological parents have allergies. Family members may differ widely in the kinds of things they are allergic to.