Diphenhydramine

Antihistamine (older type)
ALSO SOLD WITHOUT PRESCRIPTION

Diphenhydramine is a antihistamine (older type) found in 2 medicines sold in India, such as Vicks Action 500 Advanced, Benadryl Cough Formula. Below: what it is for, how it works, how to take it, side effects, interactions and pregnancy advice.

What it is used for

Calms cough and allergy symptoms such as sneezing and runny nose.

How it works

An older, strongly sedating antihistamine used in cough syrups and for allergy and itching.

How to take it

Take as directed on the pack. Do not give to young children unless a doctor advises. Avoid driving or operating machinery.

Common side effects

  • Drowsiness
  • Dry mouth
  • Dizziness
  • Constipation
  • Blurred vision

Get medical help straight away if

  • Confusion (especially in older people)
  • Fast heartbeat
  • Inability to pass urine
  • Seizures with overdose

Be careful

Causes marked drowsiness; avoid driving and alcohol.

Other medicines and interactions

Greatly increases drowsiness with alcohol, opioids and sedatives. Adds to side effects of other anticholinergic medicines.

Pregnancy and breastfeeding

Ask a doctor before using in pregnancy. Avoid while breastfeeding because it can make babies drowsy and reduce milk.

Combination medicines that contain Diphenhydramine (2)

Benadryl Cough FormulaVicks Action 500 Advanced

Common questions

What is Diphenhydramine used for?

Calms cough and allergy symptoms such as sneezing and runny nose.

How does Diphenhydramine work?

An older, strongly sedating antihistamine used in cough syrups and for allergy and itching.

How should I take Diphenhydramine?

Take as directed on the pack. Do not give to young children unless a doctor advises. Avoid driving or operating machinery.

What are the side effects of Diphenhydramine?

Common: Drowsiness, dry mouth, dizziness, constipation, blurred vision. Get help straight away for: Confusion (especially in older people), fast heartbeat, inability to pass urine, seizures with overdose.

Does Diphenhydramine interact with other medicines?

Greatly increases drowsiness with alcohol, opioids and sedatives. Adds to side effects of other anticholinergic medicines.

Is Diphenhydramine safe in pregnancy and breastfeeding?

Ask a doctor before using in pregnancy. Avoid while breastfeeding because it can make babies drowsy and reduce milk.

Does Diphenhydramine need a prescription in India?

It is usually sold without a prescription in India, but ask a pharmacist if you take other medicines or have a long-term illness.

Which brands contain Diphenhydramine?

Benadryl Cough Formula, Vicks Action 500 Advanced.

Sources and further reading

NHS (UK National Health Service) and MedlinePlus (US National Library of Medicine) are free, reviewed medicine guides. Brand names and doses there may differ from India.

Last reviewed 31 October 2026. Written by Satya Babu from standard prescribing information.

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For information only, not medical advice. This page is a plain-language summary written from standard prescribing information and the public guides linked below. Brands sometimes change their formula, so always check the composition printed on the pack. Doses here are typical adult doses; yours may differ. Do not start, stop or change a medicine without your doctor or pharmacist, and keep all medicines away from children. In an emergency, call 112 (India) or your local emergency number.