For localized hives or other mild skin reactions

• Take cool showers or apply cool compresses.

• Wear light clothing that doesn’t irritate your skin.

• Take it easy. Keep your activity level low.

• To relieve the itching, apply calamine lotion or take over-the-counter antihistamines, such as diphenhydramine (Benadryl) or chlorpheniramine maleate (Chlor-Trimeton).

For all other reactions, especially severe reactions, self-treatment is not recommended. Have a companion drive you to the hospital emergency department, or call 911. 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 (1-2 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 (see Follow-up).

• 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 have taken that day, what you usually take, and your allergy history.