Allergies are caused when our body responds to something in our environment that doesn't agree with us (called an allergen). Babies can be exposed to allergens through touch, eating, drinking or an injection. The body responds by releasing histamines in an attempt to fight off the allergen.
Histamines, however, can give your child coughing, sniffling, sneezing, and a runny nose. In more serious cases, a baby can experience what is called anaphylactic shock, which causes rashes, swelling and difficulty breathing; this condition can be life threatening and is considered a medical emergency.