Antihistamines

About These Medicines

Make sure you know about each of the medicines you take. This includes why you take it, how to take it, what you can expect while you're taking it, and any warnings about the medicine.

The information provided here is general. So be sure to read the information that came with your medicine. If you have any questions or concerns, talk to your pharmacist or doctor.

What are some examples?

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)

Why are antihistamines used?

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

What about side effects?

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.

General information about side effects

All medicines can cause side effects. Many people don't have side effects. And minor side effects sometimes go away after a while.

But sometimes side effects can be a problem or can be serious.

If you're having problems with side effects, talk to your doctor. Your doctor may be able to lower your dose or change to a different medicine.

Always be sure you get specific information on the medicine you're taking. For a full list of side effects, check the information that came with the medicine you're using. If you have questions, talk to your pharmacist or doctor.

What are some cautions about NSAIDs?

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.^{footnote 1} 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.

General cautions for all medicines

Allergic reactions.

All medicines can cause a reaction. This can sometimes be an emergency. Before you take any new medicine, tell the doctor or pharmacist about any past allergic reactions you've had.

Drug interactions.

Sometimes one medicine may keep another medicine from working well. Or you may get a side effect you didn't expect. Medicines may also interact with certain foods or drinks, like grapefruit juice and alcohol. Some interactions can be dangerous.

Harm during pregnancy or breastfeeding.

If you are pregnant, trying to get pregnant, or breastfeeding, ask your doctor or pharmacist if all the medicines you take are safe.

Other health problems.

Before taking a medicine, be sure your doctor or pharmacist knows about all your health problems. The medicine for one health problem may affect another health problem.

Always tell your doctor or pharmacist about all the medicines you take. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. That information will help prevent serious problems.

Always be sure you get specific information on the medicine you're taking. For a full list of warnings, check the information that came with the medicine you're using. If you have questions, talk to your pharmacist or doctor.