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Antihistamines

If you are having any symptoms or have any questions, please call 811 to speak with a registered nurse 24 hours a day.

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 healthcare provider.

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 healthcare provider if antihistamines are safe for you. Ask your healthcare provider 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 in 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 healthcare provider or pharmacist which OTC antihistamine is best for you based on your symptoms.

If you have severe allergies or allergies that affect you year-round, tell your healthcare provider. It could be that you need a prescription allergy medication. The difference between these at OTCs is that prescription antihistamines can come in higher doses.

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 drugs, such as erythromycin (an antibiotic), itraconazole or ketoconazole. When your healthcare provider 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 which medicines you shouldn’t take with a prescription antihistamine. If you aren’t sure, ask the pharmacist or your healthcare provider 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 healthcare provider 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.

This information provides a general overview and may not apply to everyone. Talk to your healthcare provider to find out if this information applies to you and to get more information on this subject.

Written by familydoctor.org editorial staff.

Copyright (c) by the American Academy of Family Physicians

Nova Scotia Telecare, Reviewed by Clinical Services Working Group, November 2021

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