For more severe reactions, self-treatment is not recommended. Call your health-care provider or 911, depending on the severity of your symptoms. If you have symptoms of anaphylaxis, here's what you can do while waiting for the ambulance: try to stay calm. If you can identify the cause of the reaction, prevent further exposure.

Take an antihistamine (one to two tablets or capsules of diphenhydramine [Benadryl]) if you can swallow without difficulty. If you are wheezing or having difficulty breathing, use an inhaled bronchodilator such as albuterol (Proventil) or epinephrine (Primatene Mist) if one is available. These inhaled medications dilate the airway.

If you are feeling light-headed or faint, lie down and raise your legs higher than your head to help blood flow to your brain.

If you have been given an epinephrine kit, inject yourself as you have been instructed. The kit provides a premeasured dose of epinephrine, a prescription drug that rapidly reverses the most serious symptoms. Bystanders should administer CPR to a person who becomes unconscious and stops breathing or does not have a pulse.

If at all possible, you or your companion should be prepared to tell medical personnel what medications you take and any known allergies.

Generally, treatment of a drug allergy falls into three categories:

* Mild allergy (localized hives and itching)

o Treatment is aimed at caring for the symptoms and stopping the reaction caused by the drug.

o Medications prescribed may include antihistamines, such as diphenhydramine (Benadryl)

o You may be advised to stop taking the medication that caused the allergy.

* Moderately severe allergy (all-over hives and itching)

o Treatment is aimed at caring for the symptoms and stopping the reaction.

o Usually the offending medication is stopped.

o Medications prescribed may include antihistamines such as diphenhydramine (Benadryl)), oral steroids (prednisone), or histamine blockers such as cimetidine (Tagamet), famotidine (Pepcid), or ranitidine (Zantac).

* Severe allergy (shortness of breath, throat tightness, faintness, severe hives, involvement of many organ systems)

o Treatment includes strong medications to quickly reverse the dangerous chain of events.

o The offending medication is stopped immediately.

o Medications prescribed may include antihistamines such as diphenhydramine (Benadryl), oral or IV steroids such as prednisone or methylprednisolone (Solu-Medrol), or histamine blockers such as cimetidine (Tagamet), famotidine (Pepcid), or ranitidine (Zantac).

Depending on the severity of other symptoms, other medications may be used including epinephrine (also called adrenaline), which is inhaled, given by IV, or injected under the skin. If your reaction is severe, you may need to be admitted to the hospital for continued therapy and observation.