Examples

Antihistamines can be taken by mouth or applied directly to the skin.

How It Works

Antihistamines block histamines-chemicals that cause itching and other responses to allergic substances.

Why It Is Used

Antihistamines can reduce itching and scratching from chickenpox (varicella) blisters. Scratching of blisters can cause skin infection and scars. Some skin infections can be serious.

How Well It Works

Antihistamines taken by mouth may help prevent you or your child from scratching the rash and blisters, especially during sleep.

Side Effects

Side effects of antihistamines include:

• Irritability and restlessness (particularly in children).
• Feeling sleepy and weak.
• Blurred vision.
• Difficulty passing urine.
• Stomach pains.
• Dry nose, mouth, and throat.

In very rare cases, antihistamines may cause a person to see and hear things that are not there (hallucinations), have tremors, or go into a coma.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Some experts believe that the chemical histamine is not responsible for the itching of chickenpox and that the sedating effect of antihistamines is really what helps the itching.

Some antihistamines, such as Benadryl, can be purchased without a prescription.

For children, avoid using antihistamines that are applied directly to the skin, such as diphenhydramine in Caladryl. It is difficult to know how much of the medicine is being absorbed into their bodies. You may accidentally apply too much medicine, which can be harmful.

Check with a child's health professional before giving the child oral antihistamines. Antihistamines have side effects that can cover up signs of serious complications of chickenpox. Some of these side effects include feeling sleepy and having hallucinations.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.