What Is an Allergy?
Parents often don't realize that symptoms such as runny nose, rash, upset stomach, or crankiness can signal an allergy. Instead they chalk these things up to a chronic cold, infant acne, delicate stomach, or just a fussy baby. Most of the time these symptoms -- especially if they're short-lived -- are the result of a cold or another passing ailment. However, in some cases the cause is allergies.
When baby has an allergic reaction, it's the result of an inappropriate response by his immune system. The immune system is programmed to fight off illness, but sometimes it reacts to a harmless substance, like pollen, as if it were an invading parasite, virus, or bacteria. To fight back, the immune system overproduces protective proteins called antibodies. This overproduction causes swelling and inflammation of tissues -- the nasal passages, for example. Your baby's allergic reaction can recur whenever he's exposed to whatever triggered it.
The tendency to get allergies is hereditary, but specific allergies are not. For example, if you're allergic to penicillin, your child may develop allergies although he might not be allergic to penicillin.