What is antihistamines?

Antihistamine medicines may relieve allergy symptoms and itching. Many are available without a prescription. Nondrowsy antihistamines include cetirizine (Zyrtec) and loratadine (Claritin). Antihistamines like diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton) can cause side effects and make you sleepy. They may not be safe for young children, older adults, or people with certain health problems.

Here are some examples of antihistamines. For each item in the list, the generic name is first, followed by examples of brand names.

• azelastine (Aleron, Astepro, Olopan)
• cetirizine (Zyrtec)
• chlorpheniramine (Chlor-Trimeton)
• diphenhydramine (Benadryl)
• loratadine (Claritin)

Antihistamines that are taken by mouth (oral) work better than those that are applied directly to the skin (topical) because a pill or capsule contains a specific dose of medicine. The dose in a cream or ointment depends on how much is applied at one time and is harder to control. Too much antihistamine absorbed through the skin can be toxic, especially to children. The use of cream or ointment antihistamines is not reliable and not recommended.

Don't give any antihistamines to your child unless you've checked with the doctor first. The U.S. Food and Drug Administration (FDA) recommends not using over-the-counter cough and cold medicines in children younger than age 2. The FDA also recommends avoiding these medicines for children younger than age 4. If you use these medicines, always follow the directions about how much to use based on age and, in some cases, weight.

Read and follow all instructions on the label.

Do not take oral antihistamines when you are driving, are operating machinery, or need to be alert. They can make you sleepy.

Use caution if you have other health problems, such as glaucoma, epilepsy, or an enlarged prostate. Antihistamines can cause your other health problems to get worse. And they may interact with other medicines, such as antidepressants, sedatives, and tranquilizers. Read the package carefully, and ask your pharmacist or doctor to help you choose a medicine that will not cause problems.

Antihistamines are often combined with a decongestant in one product. These medicines may not be safe for young children or for people who have certain health problems.

Antihistamines help relieve sneezing, a runny nose, itching, and watery eyes.

Nondrowsy antihistamines such as cetirizine (Zyrtec) and loratadine (Claritin) are safe for most people and cause few side effects.

Antihistamines like diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton) may have more side effects. Side effects may include:

• Tiredness.
• Headache.
• Blurred vision.
• Dry eyes.
• Constipation.
• Problems urinating.
• Confusion.
• Memory problems.
• Heart problems.

If you have side effects, stop taking the medicine and call your doctor.

Antihistamines like diphenhydramine and chlorpheniramine may not be safe for young children, older adults, or people who have certain health problems. They may make young children very sleepy or may stimulate the nervous system, causing hyperactivity.