An allergic reaction occurs when the body’s immune system responds aggressively to a particular protein or proteins. Allergic reactions can be caused by protein in substances such as food, insect stings, latex or medication. These proteins are known as allergens. While they pose no threat to the majority of people, allergens can trigger life-threatening reactions in people with severe allergies.
The symptoms of allergic reactions vary in both type and severity. Symptoms can also develop at different rates, sometimes getting worse very quickly. The most severe reaction, called anaphylaxis, can be fatal.
The most common symptoms of an allergic reaction are:
- flushed or pale face, hives, rash, red and itchy skin;
- swelling of the eyes, face, lips, throat and tongue;
- trouble breathing, speaking or swallowing;
- anxiety, distress, sense of doom, weakness, fainting, paleness;
- cramps, diarrhea, vomiting; and
- drop in blood pressure, shock, rapid heart beat, loss of consciousness.
Last modified: February 19, 2020