Anaphylaxis Make an Appointment Find a Doctor Ask a Question Reviewed by Rafeul Alam, MD, PhD (July 01, 2012) Anaphylaxis is a systemic (whole body), life-threatening allergic reaction, and is the most severe type of allergic reaction. Fortunately, it is very rare and many people with allergies will not experience anaphylaxis. Anaphylaxis can be caused by allergies to many environmental agents. The common ones are: Medicines Insect stings Foods Latex In addition to allergens, physical exertion can cause anaphylaxis. This is known as exercise-induced anaphylaxis. Some forms of anaphylaxis are called idiopathic (unknown cause). Doctors diagnose this condition when they rule out the contribution from environmental factors. Symptoms Symptoms of anaphylaxis often appear quickly. They often appear within minutes of exposure to an allergen (a substance which causes an allergic reaction). In a few cases, reactions have been delayed as much as 12 to 24 hours. Symptoms of anaphylaxis include: Breathing difficulties, coughing, chest tightness or wheezing Dizziness, fainting, rapid or weak heartbeat Swelling in the mouth and throat or trouble swallowing Flushing, itching, hives or a feeling of warmth Vomiting, diarrhea or stomach cramping along with some of the symptoms mentioned above Programs & Services Allergy Treatment Programs (Adult) Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.