A person may develop sensitivity and anaphylaxis to a substance that he or she has been exposed to multiple times in the past without a reaction. Numerous other substances can cause anaphylaxis in a sensitized person. Often, the cause is unknown. Most anaphylactic reactions will involve the skin. Look for swelling in the face, eyelids, lips, tongue, throat, hands, and feet.
Hives can cause severe itching.
Swelling narrows the person's airways. The person may have difficulty breathing, wheezing, and chest tightness. Upper airway involvement causes hoarseness, coughing, nasal congestion, and sneezing. A person experiencing anaphylaxis may have a rapid heart rate, low blood pressure, shock, dizziness, and loss of consciousness. The person may have difficulty swallowing, nausea, vomiting, diarrhea, abdominal cramping and bloating, anxiety, weakness, and confusion.