Your immune system is responsible for defending the body against bacteria and viruses. In some cases, your immune system will defend against substances that typically don’t pose a threat to the human body.

The look and feel of an allergic reaction depends on the body part involved and the severity of the reaction.

Causes, Symptoms and Treatments

Some reactions affect many areas, others affect just one area. Reactions to the same allergen vary by individual.

  1. 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.
  2. 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.
  3. 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.
  4. Because allergic reactions can progress and worsen in minutes, medical attention is always recommended for all but the most minor and localized symptoms.
  5. If the symptoms of your reaction get worse over a few days, or if they do not get better with recommended treatment and removal of the allergen, call your health care provider.
  6. Tell your health care provider if you have any allergic symptoms after using a drug or other treatment he or she prescribed for you (see Drug Allergy).
  7. Allergic reactions can be dangerous. Sudden, severe, widespread reactions require emergency evaluation by a medical professional.
  8. For typical allergic reactions, your health care provider will examine you and ask you questions about your symptoms and their timing. Blood tests and x-rays are not needed except under unusual circumstances.
  9. In case of severe reaction, you will be evaluated quickly in the emergency department. The first step for the health care provider is to judge the severity of the allergic reaction.
  10. Avoid triggers! If you know you have an allergic reaction to peanuts, for example, do not eat them. Go out of your way to avoid foods prepared with or around peanuts.
  11. Small reactions with mild symptoms usually respond to nonprescription allergy medications.

An allergic reaction is the body’s way of responding to an “invader.” When the body senses a foreign substance, called an antigen, the immune system is triggered.

The immune system normally protects the body from harmful agents such as bacteria and toxins. Its overreaction to a harmless substance (an allergen) is called a hypersensitivity, or allergic, reaction.