Diphenhydramine (Benadryl)




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:

  • short-term sleep problems (insomnia), including when a cough, cold or itching is keeping you awake at night
  • cough and cold symptoms
  • hay fever
  • eczema, hives (urticaria) and insect bites and stings

You can buy diphenhydramine from pharmacies and it is 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.

  • 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.
  • You can become dependent on diphenhydramine if you take it continuously for a period of time. 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.
  • When diphenhydramine is mixed with other medicines, brand names include Benylin Chesty Coughs, Benylin Children’s Night Coughs, Covonia Night Time Formula, Panadol Night Pain and Unicough.