Diphenhydramine is an antihistamine medicine that relieves the symptoms of allergies. It's known as a drowsy (sedating) antihistamine and is more likely to make you feel sleepy than other antihistamines.
It's used for:
- hay fever
- eczema, hives (urticaria) and insect bites and stings
- short-term sleep problems (insomnia), including when a cough, cold or itching is keeping you awake at night
You can buy diphenhydramine from pharmacies and it's also available on prescription.
It comes as tablets and a liquid that you swallow. For skin allergies like hives or bites and stings it's also available as a cream. The cream is much less likely to make you feel sleepy than the tablets or liquid.
You can also buy it mixed with other medicines, such as levomenthol, paracetamol, pseudoephedrine, ammonium chloride and dextromethorphan to treat cough and cold symptoms.
Key facts
- To help you sleep, you'll usually take diphenhydramine 20 minutes before you go to bed. It normally takes about 30 minutes to work.
- Common side effects include feeling sleepy, dizzy or unsteady on your feet. You may also have difficulty concentrating and have a dry mouth. Do not drive or ride a bike if it makes you feel sleepy or dizzy.
- You can become dependent on diphenhydramine tablets or liquid if you take it for too long without a break. It may also stop working as well. Speak to your doctor if you need to take it for more than 2 weeks.
- Do not drink alcohol while taking diphenhydramine. Alcohol increases the risk of side effects.
- Brand names of medicines that contain diphenhydramine mixed with other medicines include Benylin Chesty Coughs, Benylin Children's Night Coughs, Bell's Dual Action Chesty Cough, Covonia Night Time Formula, Numark Chesty Cough Expectorant and Panadol Night Pain.