What are antihistamines?

Antihistamines are medicines that help stop allergy symptoms. These symptoms include:

  • itchy eyes
  • sneezing
  • runny nose or congestion
  • skin rashes such as hives.

They are normally taken by mouth. They come in tablets, capsules, chewable tablets, and liquids. Many people buy them over the counter (OTC) at a store. You can also get them through a prescription from your doctor.

Antihistamines are generally considered safe for most people. This includes adults, children over the age of 2, and older people. If you are pregnant or breastfeeding, ask your doctor if antihistamines are safe for you. Ask your doctor if you can take antihistamines if you have a chronic disease or condition. This includes heart disease, diabetes, or high blood pressure.

Path to improved health

You can take antihistamines different ways, depending on your symptoms. Some people take them only when they have symptoms. Others experience symptoms every day, so they take the antihistamine every day. Sometimes people take them before they are going to be exposed to something they are allergic to. This could include an animal (such as cats or dogs) or certain kinds of plants or flowers.

There are many different brands of antihistamines that you can buy over the counter. Some work in different ways. For example, some are designed to work for 4 to 6 hours. Others last for 12 to 24 hours. Make sure you read the label carefully. Follow the directions for how often to take the antihistamine.

Ask your doctor which OTC antihistamine is best for you based on your symptoms.

Why did my doctor give me a prescription when I could buy an over-the-counter antihistamine?

Compared to OTC medicines, prescription antihistamines are less likely to have side effects. These can include drowsiness, dry mouth, or blurry vision. They may be better for some people, including:

  • Older people.
  • Children during school hours.
  • People who work with machinery or drive cars.

Things to consider

Like most medicines, antihistamines can cause side effects. The most common include:

  • drowsiness
  • dizziness
  • dry mouth
  • blurry vision
  • decreased appetite
  • feeling nervous, irritable, or excited.

Some types of antihistamines can cause sleepiness. Do not drink alcohol when taking antihistamines.

Can I take my prescription antihistamine with other medicines?

You shouldn’t take prescription antihistamines if you also are taking certain other prescription medicines. These include erythromycin (an antibiotic) or certain medicines used to treat fungal infections. These include itraconazole or ketoconazole. When your doctor gives you a prescription, always ask if it’s safe to use with the other medicines you’re taking. Your pharmacist can also tell you what is safe to take. If you aren’t sure, ask the pharmacist or your doctor before taking another medicine.

Can I share my prescription antihistamines with friends who have allergies?

No. You should never share a prescription medicine with another person. Your doctor has examined you and has picked a medicine that is right only for your problem. Some antihistamines can cause serious side effects if they are given to people who are taking another medicine, or who should not take antihistamines for another reason.

Questions to ask your doctor

  • Do I need an antihistamine?
  • Can I take one over the counter, or do I need a prescription?
  • Which over-the-counter type of antihistamine is the best for my symptoms?
  • What are the side effects of this type or brand?
  • Is there anything I should avoid doing while I’m taking an antihistamine?
  • How long should I take it?