The look and feel of an allergic reaction depends on the body part involved and the severity of the reaction. Some reactions affect many areas, while others affect just one area. Reactions to the same allergen vary by individual.

• Anaphylaxis is the term for any combination of allergic symptoms that is rapid, or sudden, and potentially life-threatening. Call an ambulance immediately if you suspect anaphylaxis.
  • One sign of anaphylaxis is shock. Shock has a very specific meaning in medicine: The organs of the body are not getting enough blood because of dangerously low blood pressure. Shock may lead rapidly to death. The person in shock may be pale or red, sweaty or dry, confused, anxious, or unconscious.
  • Breathing may be difficult or noisy, or the person may be unable to breathe.
• Shock is caused by sudden dilation of many or large blood vessels. This is brought on by the action of the mediators. If the drop in blood pressure is sudden and drastic, it can lead to unconsciousness, even cardiac arrest and death.

• Symptoms of an allergic reaction include any, some, or many of these:
  • Skin: redness, itching, swelling, blistering, weeping, crusting, rash, eruptions, or hives (itchy bumps or welts)
  • Lungs: wheezing, tightness, cough, or shortness of breath
  • Head: swelling of the face, eyelids, lips, tongue, or throat; headache
  • Nose: stuffy nose, runny nose (clear, thin discharge), sneezing
  • Eyes: red (bloodshot), itchy, swollen, or watery
  • Stomach: pain, nausea, vomiting, diarrhea, or bloody diarrhea