Like all medicines, chlorphenamine can cause side effects, although not everyone gets them.
Children and people aged over 65 have more chance of getting some side effects, such as feeling restless or excited.
Common side effects of chlorphenamine
These common side effects of chlorphenamine happen in more than 1 in 100 people. There are things you can do to help cope with them:
Feeling sleepy during the daytime
Drowsiness usually wears off 4 to 6 hours after a dose. Do not drive, ride a bike or use tools or machinery if you're feeling this way.
Feeling sick (nausea)
Try taking your tablets with food. It may also help if you do not 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 does not go away or is troubling you, do not take any more chlorphenamine and speak to a pharmacist or your doctor.
Do not drive or ride a bike if you're feeling dizzy or unable to concentrate.
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 the headaches do not go away or are severe.
Blurred vision
Do not drive, ride a bike or use tools or machinery while this is happening.
This is usually only a mild problem but if it bothers you, speak to your pharmacist or doctor as you may need to change your treatment.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
Serious side effects
Call your doctor or call 111 straight away and stop taking chlorphenamine if:
- the whites of your eyes turn yellow, or your skin turns yellow although this may be less obvious on brown or black skin – these can be signs of liver problems
- you are bruising or bleeding more easily than normal
- you have difficulty peeing
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to chlorphenamine.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Other side effects
These are not all the side effects of chlorphenamine. For a full list, see the leaflet inside your medicine packet.
Reporting side effects
You can report any suspected side effect using the Yellow Card safety scheme.
Visit the Yellow Card website for more information about reporting side effects.