What is anaphylactic shock?

Anaphylactic shock (also called anaphylaxis) is a rapid and severe allergic reaction, and one of the scariest health emergencies a parent can face. It starts when the immune system mistakenly responds to a harmless substance as if it were a serious threat. This triggers the release of histamine and other chemicals that cause a number of symptoms — some of them life-threatening.

The symptoms in a baby include:

    * Swelling of the skin, lips, throat, tongue, or face
    * Wheezing or severe breathing problems
    * Rapid pulse or irregular heartbeat
    * Hives
    * Loss of consciousness
    * Vomiting
    * Diarrhea
    * Extremely pale skin and sweating, skin redness, or blue skin color

Symptoms usually appear within two hours after exposure to the substance — sometimes within minutes — although it's possible for symptoms to appear up to four hours later.

Anaphylaxis is uncommon in babies under 6 months, in part because they haven't been exposed to many allergens, especially food allergens. In general, it takes more than one exposure to an allergen for a reaction to occur, and it can take until the toddler years for some allergies to develop. Still, anaphylaxis has been reported in babies as young as 1 month old and in children with no known previous exposure to the allergen.