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Chlorphenamine (including Piriton)

On this page

  1. About chlorphenamine
  2. Key facts
  3. Who can and cannot take chlorphenamine
  4. How and when to take it
  5. Side effects
  6. How to cope with side effects
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions

1. About chlorphenamine

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.

2. Key facts

  • 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.

3. Who can and cannot take chlorphenamine

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

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

Chlorphenamine is not 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.

4. How and when to take it

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


If you have bought chlorphenamine or any medicine containing chlorphenamine from a pharmacy, follow the instructions that come with the packet, or ask your pharmacist for advice.

If you or your child's symptoms don't get better within a few days, talk to a doctor.

Dosage and strength

Chlorphenamine comes as 4mg tablets and as a liquid that you swallow. If you're taking liquid chlorphenamine, follow the instructions that come with the medicine for how much to take.

If you're taking chlorphenamine tablets, the usual dose for allergies in adults and children aged 12 years and older is 4mg every 4 to 6 hours. Do not take more than 6 tablets (24mg) in 24 hours.

Doses are lower for children and babies, and they may take it less often. Your doctor will use your child's age to work out the right dose.

If you have bought chlorphenamine from a pharmacy for a child aged over 1 year, follow the instructions on the packet or ask the pharmacist.

If you're over 65 years old, do not take more than 3 tablets (12mg) in 24 hours as you're more likely to get side effects.

When used for coughs and colds, chlorphenamine is mixed with other medicines in a liquid that you swallow. Follow the instructions on the bottle or packaging or how much to take.

How to take it

You can take chlorphenamine with or without food.

Swallow your chlorphenamine tablets with a drink of water, milk or juice. 4mg tablets can be broken in half for children and people taking lower doses.

Chlorphenamine liquid may be easier for children to take than tablets. The medicine will come with a plastic syringe or spoon to help you measure out the right dose.

If you don't have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not give the right amount.

When to take it

Only take chlorphenamine when you need to.

  • for allergies, you may only need to take chlorphenamine on a day you have symptoms, such as if you have been exposed to a trigger like animal hair
  • for hay fever, you may need to take it regularly to prevent symptoms during spring and summer

What if I forget to take it?

Take your forgotten dose as soon as you remember, unless it's nearly time for your next dose. Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

If you have accidentally taken too much chlorphenamine, you may:

  • feel very sleepy
  • feel nervous or restless
  • feel or be sick (nausea or vomiting)
  • get blurred vision
  • get a very fast, uneven or pounding heartbeat (palpitations)

In serious cases, you can have fits or become unconscious and may need emergency treatment in hospital.

Urgent advice: Call your doctor straight away if:

  • you take too much chlorphenamine

If you need to go to a A&E, do not drive yourself - get someone else to drive you or call for an ambulance.

Take the chlorphenamine packet or leaflet inside it, plus any remaining medicine, with you.

5. Side effects

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.

Immediate action required: Call 999 or go to A&E now if:
  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of chlorphenamine. For a full list, see the leaflet inside your medicine packet.


You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

6. How to cope with side effects

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.

7. Pregnancy and breastfeeding

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.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

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.

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

9. Common questions

How does chlorphenamine work?

Chlorphenamine is a medicine called an antihistamine. It's classed as a drowsy (sedating) antihistamine.

When you come into contact with something you're allergic to, such as pollen, animal hair or fur, house dust or insect bites and stings, your body produces a chemical called histamine.

Usually, histamine is a useful substance, but in an allergic reaction it causes symptoms including itchy, watery eyes, a running or blocked nose, sneezing and skin rashes.

Chlorphenamine blocks the effects of histamine and so reduces these symptoms.

How long does it take to work?

You should start to feel better within 30 minutes to an hour.

How long can I take it for?

It depends on why you're taking it. You may only need to take chlorphenamine for a short time or as a one-off dose.

If you're taking it for a cough or cold and your symptoms last for more than 3 weeks, it's a good idea to see your doctor so they can investigate the cause.

If you have a reaction to an insect bite or a medicine, you may only need to take chlorphenamine for a day or two.

You may need to take it for longer if you're taking it to prevent symptoms from hay fever when the pollen count is high.

Talk to your doctor or pharmacist if you're unsure how long you need to take chlorphenamine for.

Is it safe to take chlorphenamine for a long time?

Chlorphenamine is unlikely to do you any harm if you take it for a long time.

But it's best to take chlorphenamine only for as long as you need to.

Talk to your doctor about how long you can take it for.

Is it possible to be addicted to chlorphenamine?

No, chlorphenamine isn't known to be addictive.

What's the difference between chlorphenamine and other antihistamines?

Chlorphenamine is known as a drowsy antihistamine as it can make you feel sleepy.

Non-drowsy antihistamines are less likely to have this effect. These include cetirizine, fexofenadine or loratadine.

Most people prefer to take a non-drowsy antihistamine as it's less likely to interfere with their everyday routine.

You might choose to take a drowsy antihistamine, if you have a symptom that's keeping you awake, such as itchy skin.

There isn't enough information to say whether one antihistamine is better than another for treating allergies.

Sometimes you need to try a few before you find one that works best for you.

Can you take more than one antihistamine at a time?

If you have a very itchy rash, your doctor may advise that you take 2 different antihistamines for a few days.

As well as taking a non-drowsy antihistamine during the day (such as fexofenadine, cetirizine or loratadine), your doctor may recommend a drowsy antihistamine at night time if itching is making it difficult for you to fall sleep.

Do not take another drowsy antihistamine together with chlorphenamine. It'll make you very tired and sleepy.

Other drowsy antihistamines include diphenhydramine (Nytol), hydroxyzine (Atarax or Ucerax) and promethazine (Phenergan).


Do not take 2 antihistamines together unless you have been told to by your doctor.

Can I take chlorphenamine with painkillers?

Yes, you can take chlorphenamine together with painkillers like paracetamol or ibuprofen that you buy from the pharmacy or supermarket.

But if you take chlorphenamine with painkillers that contain codeine (such as co-codamol) or other prescription painkillers, you may feel very tired and sleepy.

Do not drive, ride a bike or operate machinery or tools if this happens to you.

Will it help me sleep?

Doctors sometimes recommend taking drowsy antihistamines, like chlorphenamine, for a short time to help you sleep if your allergy symptoms keep you awake at night.

But do not take it just for sleep problems without talking to you doctor first, as there may be something better you can take.

If you're having difficulty sleeping (insomnia), there are a number of things you can try to help yourself get a good night's sleep:

  • set regular times for going to bed and waking up
  • relax before bedtime - try taking a warm bath or listening to calming music
  • use thick curtains or blinds, an eye mask and earplugs to stop you being woken up by light and noise
  • avoid caffeine, cigarettes or vapes, alcohol, heavy meals and exercise for a few hours before bed time
  • do not watch TV or use phones, tablets or computers before going to bed
  • do not nap during the day
  • make a list of your worries and any ideas for how to solve them before you go to bed. This can help you forget about them until the morning.

If this doesn't work, speak to your doctor.

Can I drink alcohol with it?

Avoid drinking alcohol while you're taking chlorphenamine, as it can make you feel very sleepy.

Is there any food or drink I need to avoid?

You can eat and drink normally while taking chlorphenamine.

Will it affect my fertility?

There's no firm evidence to suggest that taking chlorphenamine will reduce fertility in either men or women.

But speak to a pharmacist or your doctor before taking it if you're trying to get pregnant.

Will it affect my contraception?

Chlorphenamine does not affect any type of contraception, including the combined pill and emergency contraception.

Can I drive or ride a bike with it?

Do not drive a car or ride a bike if chlorphenamine makes you sleepy during the daytime, gives you blurred vision or makes you feel dizzy, clumsy or unable to concentrate or make decisions.

This may be more likely when you first start taking chlorphenamine, but could happen at any time (for example, when starting another medicine).

It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.

GOV.UK has more information on the law on drugs and driving.

Talk to your doctor or pharmacist if you're unsure whether it's safe for you to drive while taking chlorphenamine.

Can lifestyle changes help with hay fever and other allergies?

If you have hay fever, it'll help if you don't spend too much time outside when the pollen count is high.

Tips for when you're outside

  • Don't cut grass or walk on grass.
  • Wear wraparound sunglasses to stop pollen getting into your eyes.
  • Put Vaseline around your nostrils to help trap pollen.
  • Shower and change your clothes after you have been outside to wash off pollen.

Tips for when you're inside

  • Keep windows and doors shut as much as possible.
  • Vacuum regularly and dust with a damp cloth.
  • Don't keep fresh flowers in the house.
  • Don't smoke or be around smoke as it makes hay fever symptoms worse.

The best way to prevent any sort of allergic reaction is to avoid the substance that you're allergic to, if you can.

There are some practical steps you can follow to help you prevent allergies.