Common symptoms of allergies

There are many symptoms of food allergies, including nausea, vomiting, diarrhea, constipation, indigestion, headaches, skin rashes or hives, itching, shortness of breath (including asthma attacks), and, in severe cases, widespread swelling of the skin and mucous membranes. Swelling in the mouth or throat is potentially fatal because it can block the airways to the lungs. In the most severe cases, anaphylactic shock-a life threatening collapse of the respiratory and circulatory system-may develop.

Allergies usually provoke the same symptoms each time, but many factors affect intensity, including how much of the offending food was eaten, and how it was prepared. Some people can tolerate small amounts of an offending food; others are so hypersensitive that they react to even a minute trace.