Chlorphenamine (Pollenase antihistamine tablets)

How does it work?

Pollenase anthistamine tablets contain the active ingredient chlorphenamine maleate (previously spelt chlorpheniramine in the UK), which is a type of medicine called a sedating antihistamine. (NB. Chlorphenamine is also available without a brand name, ie as the generic medicine.) Chlorphenamine works by preventing the actions of histamine.

Histamine is a substance produced by the body as part of its defence mechanisms. It is stored in cells called mast cells, in almost all tissues of the body. When the body reacts to a foreign substance (known as an allergen, eg flower pollen), the mast cells are stimulated by the allergen and release their stores of histamine.

The released histamine then binds to its receptors (H1 receptors), causing a chain reaction that results in allergic symptoms. It causes an increase in blood flow to the area of the allergy, and the release of other chemicals that add to the allergic response.

All this results in the symptoms of an allergic reaction. In hayfever, this causes inflammation of the nose, eyes or airways and results in itchy watery eyes, a runny nose, sneezing and nasal congestion. Histamine is also responsible for the symptoms of allergic and itchy rashes, and allergic reactions to foods, medicines or insect bites. It can also cause more severe allergic reactions such as angioneurotic oedema, which involves severe swelling of the eyes, lips, tongue or throat.

Chlorphenamine works by blocking histamine H1 receptors. It does not prevent the actual release of histamine from mast cells, but prevents it binding to its receptors. This in turn prevents the release of other allergy chemicals and increased blood supply to the area, and provides relief from the typical symptoms of allergies.

Chlorphenamine is called a sedating antihistamine because it enters the brain in significant quantities and causes drowsiness.

The antihistamine action and the fact that it causes drowsiness also make chlorphenamine useful for relieving itching caused by chickenpox. It may be especially helpful for itching that is worse at night. This is often the case in children, who notice itching less during the day when they are active, but are bothered by it at night when they are still and have nothing else to focus on.

What is it used for?

  • Relieving the symptoms of allergic conditions such as hayfever, nettle rash (urticaria), food allergies and reactions to insect bites or medicines.
  • Relieving the symptoms of a more serious allergic reaction called angioneurotic oedema, which causes swelling of the eyes, lips, tongue or throat.
  • Relieving itching associated with chickenpox.

How do I take it?

  • Adults, adolescents and children aged 12 years and over should take one Pollenase antihistamine tablet every four to six hours, up to a maximum of six tablets in 24 hours. Elderly people should avoid taking more than three tablets in 24 hours as they may be more susceptible to the potential side effects of this medicine.
  • Children aged 6 to 12 years can be given half a Pollenase antihistamine tablet every four to six hours, up to a maximum of six doses (three tablets in total) in 24 hours.
  • Pollenase antihistamine tablets are not recommended for children under six years of age. Chlorphenamine syrup is available for this age group.
  • The tablets can be taken either with or without food.
  • Do not exceed the recommended dose.
  • If symptoms persist despite treatment, seek medical advice from your doctor or pharmacist.


  • This medicine may cause drowsiness, blurred vision or dizziness. If affected do not drive or operate machinery. If children are affected they should avoid potentially hazardous activities such as riding bikes or climbing trees.
  • You should not drink alcohol while taking this medicine as it is likely to make any drowsiness or dizziness worse.
  • If you are due to have any skin prick or patch tests to diagnose allergies you should stop taking your antihistamines at least 48 hours before the tests. This is because antihistamines can prevent or lessen the skin reactions that indicate an allergy, and so can make the test results unreliable.

Use with caution in

  • Elderly people (who are more prone to side effects so a lower maximum dose is recommended - see above).
  • Children (who are also more prone to potential side effects).
  • Asthma.
  • Bronchitis.
  • People with widening of the airways, which may be hereditary or due to infection (bronchiectasis).
  • Men with an enlarged prostate gland (prostatic hypertrophy).
  • People who have difficulty passing urine.
  • People with raised pressure in the eye or glaucoma.
  • Epilepsy.
  • Liver disease.
  • People with severe cardiovascular disease.
  • People with very high blood pressure (severe hypertension).
  • People with an overactive thyroid gland (thyrotoxicosis).

Not to be used in

  • People who have taken a type of antidepressant called a monoamine oxidase inhibitor (MAOI, eg phenelzine, tranylcypromine or isocarboxazid) in the last 14 days.
  • Pollenase antihistamine tablets contain lactose and are not suitable for people with rare hereditary problems of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption.
  • Pollenase antihistamine tablets are not recommended for children under six years of age. Chlorphenamine syrup is available for this age group.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine during pregnancy has not been established. It should be avoided during pregnancy, unless the potential benefits to the mother outweigh any possible risk to the developing baby. This is particularly important during the first and third trimesters. As with all medicines, seek medical advice from your doctor before using this medicine if you are pregnant.
  • This medicine may pass into breast milk. It should be avoided by breastfeeding mothers unless the potential benefits to the mother outweigh any possible risk to the nursing infant. As with all medicines, seek medical advice from your doctor before using this medicine if you are breastfeeding.

Label warnings

  • This medication may cause drowsiness. If affected do not drive or operate machinery. Avoid alcoholic drink.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Sleepiness or sedation.

Common (affect between 1 in 10 and 1 in 100 people)

  • Blurred vision.
  • Dry mouth.
  • Feeling sick.
  • Difficulty concentrating.
  • Problems with coordination.
  • Dizziness.
  • Headache.
  • Fatigue.

Unknown frequency

  • Loss of appetite.
  • Disturbances of the gut such as indigestion, diarrhoea, constipation, vomiting or abdominal pain.
  • Increased energy, restlessness or nervousness (children and elderly people are more susceptible to these types of side effect).
  • Confusion.
  • Irritability.
  • Nightmares.
  • Awareness of your heartbeat (palpitations).
  • Increased heart rate.
  • Abnormal heartbeats (arrhythmias).
  • Sensation of ringing or other noise in the ears (tinnitus).
  • Low blood pressure.
  • Thickening of the mucus in the lungs.
  • Chest tightness.
  • Inflammation of the liver (hepatitis) or jaundice.
  • Skin reactions such as rash, hives or increased sensitivity to sunlight.
  • Difficulty passing urine (urinary retention).
  • Muscle twitching or weakness.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

You should not use other antihistamines in combination with this medicine. Some cough and cold medicines contain antihistamines, so always check with your pharmacist before taking other medicines in combination with this one.

This medicine should not be used by people who have taken a type of antidepressant called a monoamine oxidase inhibitor (MAOI) in the last 14 days. This is because side effects such as blurred vision, dry mouth, drowsiness or constipation may be intensified by MAOIs. MAOIs include phenelzine, isocarboxazid and tranylcypromine. For more information ask your pharmacist.

There may be an increased risk of drowsiness and sedation if this medicine is taken with any of the following (which can also cause drowsiness):

  • alcohol
  • antipsychotics, eg haloperidol, chlorpromazine
  • barbiturates, eg phenobarbital, amobarbital
  • benzodiazepines, eg diazepam, temazepam
  • other sedating antihistamines, eg hydroxyzine, promethazine
  • sleeping tablets, eg zopiclone
  • strong opioid painkillers, eg morphine, codeine, tramadol
  • tricyclic antidepressants, eg amitriptyline, nortriptyline.

There may be an increased risk of side effects such as dry mouth, blurred vision, urine retention and constipation if chlorphenamine is taken with antimuscarinic medicines that can cause these type of side effects, such as the following:

  • antimuscarinic medicines for Parkinson's symptoms, eg procyclidine, orphenadrine, trihexiphenidyl
  • antimuscarinic medicines for urinary incontinence, eg oxybutynin, flavoxate, tolterodine, propiverine, trospium
  • some antipsychotics, eg chlorpromazine, clozapine
  • antispasmodics, eg hyoscine, atropine
  • tricyclic antidepressants, eg amitriptyline, imipramine.

Chlorphenamine may oppose the effect of histamine (used to treat leukaemia) and is not recommended for people having this treatment.

Chlorphenamine may also oppose the effect of betahistine (used to treat Ménière's disease).

Chlorphenamine may increase the blood level of the antiepileptic medicine phenytoin.

Other medicines containing the same active ingredient

  • Allercalm allergy relief tablets.
  • Boots allergy relief antihistamine tablets and syrup.
  • Piriton.

Chlorphenamine tablets, oral solution and injection are also available without a brand name, ie as the generic medicine.