Allergies Health Center

Oral antihistamines are available without a prescription. Common types such as diphenhydramine (for example, Benadryl), chlorpheniramine (for example, Chlor-Trimeton), and loratadine (for example, Claritin) are used to treat allergy symptoms and itching.

Look for generic or store brands, which often cost less than name brands. For example, diphenhydramine is the generic name for the brand name Benadryl.

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. Don't give any antihistamines to your child unless you've checked with the doctor first. The use of cream or ointment antihistamines is not reliable and not recommended.

Read and follow all instructions on the label. Be sure to follow the nonprescription medicine precautions.

Do not take oral antihistamines when you are driving, operating machinery, or need to be alert because 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 problem to get worse and also 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 an antihistamine 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. Read and follow all instructions on the label.

Side effects

• In children:
  • Antihistamines may make young children sleepy or may stimulate the nervous system, causing hyperactivity. Don't give antihistamines to your child unless you've checked with the doctor first.
  • In rare cases, diphenhydramine (especially forms of it that are applied to the skin) can cause severe side effects in children, such as hallucinations, tremors, and coma.
• In older children and adults:
  • Antihistamines may cause drowsiness.
  • Weakness, blurred vision, dry nose, mouth, and throat, difficulty urinating, or stomach upset also can occur.

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

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