Chlorphenamine is an antihistamine medicine that relieves the symptoms of allergies.

It’s known as a drowsy (sedating) antihistamine. It’s more likely to make you feel sleepy than some other antihistamines.

It’s used for:

You can buy chlorphenamine from pharmacies and supermarkets. Chlorphenamine is also available on prescription.

It’s sometimes mixed with other medicines like ephedrine, pseudoephedrine or pholcodine to treat coughs and colds.

It comes as tablets or as a liquid that you swallow.

  • Avoid drinking alcohol while you’re taking chlorphenamine. Alcohol increases the risks of side effects.
  • It normally takes 30 minutes to an hour to work.
  • Common side effects include feeling sick (nausea), sleepy or dizzy. You may also have difficulty concentrating, a dry mouth, headaches or blurred vision.
  • Chlorphenamine is also known by the brands Allercalm, Allerief, Hayleve and Piriton.
  • When mixed with other medicines, it can be called Cofsed Linctus, Galpseud Plus Linctus and Haymine.

Chlorphenamine can be taken by most adults and children aged 1 month and older.

Children aged 1 to 12 months should only take chlorphenamine if prescribed by a doctor.

Chlorphenamine isn’t suitable for some people. Tell your doctor or pharmacist if you:

  • have had an allergy to chlorphenamine or any other medicines in the past
  • have an eye problem called primary angle closure glaucoma
  • have problems peeing or emptying your bladder
  • have epilepsy or another health problem that puts you at risk of fits
  • have an intolerance to, or can’t absorb, some sugars such as lactose or sucrose
  • are booked to have an allergy test – taking chlorphenamine may affect the results, so you might need to stop taking it a few days before the test. Ask a pharmacist or your doctor for advice.
  • are unable to have any alcohol – some liquid chlorphenamine products contain a very small amount of alcohol. Check the ingredients and the packaging carefully.

If you or your child has been prescribed chlorphenamine, follow your doctor’s
instructions about how and when to take it.

Like all medicines, chlorphenamine can cause side effects, although not everyone gets them.

Common side effects

Common side effects of chlorphenamine happen in more than 1 in 100 people.

Talk to your doctor or pharmacist if these side effects bother you or don’t go away:

  • feeling sleepy during the daytime
  • feeling sick (nausea)
  • feeling dizzy or difficulty concentrating
  • dry mouth
  • headaches
  • blurred vision

Children and people aged over 65 have more chance of getting some side effects, such as feeling restless, excited or confused.

Serious side effects

Tell your doctor straight away if you have:

  • yellowing of the skin or whites of the eyes – these can be signs of liver problems
  • bruising or bleeding that’s more than normal

Serious allergic reaction

In rare cases, it’s possible to have a serious allergic (anaphylaxis) reaction to chlorphenamine.

What to do about:

  • feeling sleepy during the daytime – drowsiness usually wears off 4 to 6 hours after a dose. Do not drive or use tools or machinery if you’re feeling this way.
  • feeling sick (nausea) – it may help if you don’t eat rich or spicy food while you’re taking chlorphenamine
  • feeling dizzy or difficulty concentrating – stop what you’re doing and sit or lie down until you feel better. If the feeling doesn’t go away or is troubling you, do not take any more medicine and speak to a pharmacist or your doctor.
  • dry mouth – chew sugar-free gum or suck sugar-free sweets
  • headaches – make sure you rest and drink plenty of fluids. Ask your pharmacist to recommend a painkiller. Talk to your doctor if they last longer than a week or are severe.
  • blurred vision – do not drive or use tools or machinery while this is happening. If it lasts for more than a day or two, speak to your pharmacist or doctor as they may need to change your treatment.

Chlorphenamine isn’t normally recommended in pregnancy. There’s no firm evidence that it’s harmful to an unborn baby, but there isn’t enough information to be sure it’s safe.

A non-drowsy antihistamine called loratadine is normally used first because there’s more information to say that it’s safe.

Talk to your doctor about the benefits and possible harms of taking chlorphenamine. It’ll also depend on how many weeks pregnant you are and the reason you need to take chlorphenamine.

For more information about how chlorphenamine can affect you and your baby during pregnancy, read this leaflet on the Best Use of Medicines in Pregnancy (BUMPS) website.

Chlorphenamine and breastfeeding

Chlorphenamine is sometimes used during breastfeeding, but non-drowsy antihistamines called loratadine and cetirizine are normally used first because there’s more information to say they’re safe.

Some medicines and chlorphenamine interfere with each other and increase the chances of you having side effects.

Check with your pharmacist or doctor if you’re taking:

  • a type of antidepressant called a monoamine oxidase inhibitor, such as phenelzine
  • phenytoin (an anti-epilepsy medicine)
  • any medicine that makes you drowsy, gives you a dry mouth, or makes it difficult for you to pee. Taking chlorphenamine might make these side effects worse.

Mixing chlorphenamine with herbal remedies and supplements

There might be a problem taking some herbal remedies and supplements alongside chlorphenamine, especially ones that cause side effects such as sleepiness, a dry mouth or making it difficult to pee.

How does chlorphenamine work?