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Diphenhydramine

About diphenhydramine

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 or cold, or itching, is keeping you awake at night – brand names include Nytol Original, Nytol One-a-Night and Sleepeaze
  • cough and cold symptoms – brand names include Benylin Chesty Coughs and Covonia Night Time Formula
  • hay fever – brand names include Histergan
  • eczema, hives (urticaria), insect bites and stings – brand names include Histergan

You can buy diphenhydramine from pharmacies and supermarkets. Diphenhydramine is also available on prescription.

It comes as tablets, capsules 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, capsules or liquid.

You can also buy it mixed with other medicines, such as levomenthol, paracetamol, pholcodine and pseudoephedrine, to treat cough and cold symptoms.

Key facts

  • Avoid drinking alcohol while taking diphenhydramine. Alcohol increases the risk of side effects.
  • To help you sleep, you'll usually take your medicine 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 a dry mouth.
  • Diphenhydramine is also called by the brand names Histergan, Nytol Original, Nytol One-A-Night and Sleepeaze.
  • When it's mixed with other medicines, brand names include Benylin Chesty Coughs, Benylin Children’s Night Coughs, Covonia Night Time Formula, Panadol Night Pain and Unicough.

Who can and cannot take diphenhydramine

Diphenhydramine can be taken by most adults and young people aged 16 years and above. You can sometimes give diphenhydramine to children, depending on their age and their symptoms. Ask your pharmacist for advice.

Diphenhydramine is not suitable for some people. Tell your doctor or pharmacist if you:

  • have had an allergic reaction to diphenhydramine or any other medicines in the past
  • have lung problems, such as asthma or COPD, or an illness that creates a lot of phlegm
  • have an eye problem called primary angle closure glaucoma
  • have a stomach ulcer, or a blockage in your stomach or gut
  • have kidney or liver problems
  • have problems peeing or emptying your bladder
  • have epilepsy or any other health problem that causes fits
  • have an intolerance to, or cannot absorb, some sugars such as lactose or sorbitol
  • are due to have an allergy test – diphenhydramine can affect your results, so you may need to stop taking it a few days before your test - ask a pharmacist or your doctor for advice
  • are unable to have any alcohol – some liquid diphenhydramine products contain a small amount of alcohol, so check the ingredients and the packaging carefully

Giving diphenhydramine to children

For some symptoms, you can give diphenhydramine to children over the age of 6 years. Check with your pharmacist or doctor to make sure whether a product is suitable for your child.

Warning for children

Do not give your child diphenhydramine to help them get to sleep. Diphenhydramine is only suitable for sleep problems in people aged 16 years and above.

Children aged 6 years and above can have diphenhydramine for:

  • insect bites and stings – diphenhydramine cream only
  • eczema – diphenhydramine cream only
  • cough and cold symptoms (this does not apply to all cough and cold medicines that contain diphenhydramine, so check the instructions that come with the packaging carefully)

Do not give children diphenhydramine for hay fever or other allergies until they are 12 years old or above.

How and when to take or use diphenhydramine

If you or your child have been prescribed diphenhydramine, follow your doctor's instructions about how and when to take it.

Only take or use diphenhydramine when you need it – for example if you're unable to sleep because you're worrying about something or your cold symptoms are keeping you awake.

If you've bought diphenhydramine or any medicine containing diphenhydramine from a pharmacy or supermarket, follow the instructions that come with the packet, or ask a pharmacist for advice.

The instructions will be different, depending on the type of diphenhydramine you buy - and the other medicines it's mixed with.

How much to take or use

If you're aged over 65, start with the lower dose, as you may be more likely to get side effects.

The usual dose depends on the type of diphenhydramine you're taking, and what you're taking it for:

  • short-term insomnia – diphenhydramine comes as 25mg and 50mg tablets. You'll usually take 50mg, 20 minutes before you go to bed.
  • cough and cold symptoms – diphenhydramine comes mixed with other medicines to treat the symptoms of coughs and colds. It comes as tablets, capsules and as a liquid that you swallow. The usual dose depends on the type of medicine you're taking. Check the instructions on the packaging carefully, or ask your doctor or pharmacist if you're unsure.
  • hay fever and allergies – diphenhydramine comes as 25mg and 50mg tablets. The usual dose is 25mg or 50mg, taken 3 or 4 times a day. Try to space your doses evenly throughout the day.
  • insect bites, stings and eczema – diphenhydramine comes as a cream which you use once or twice a day. You'll only need a small amount, enough for a thin layer.

How to take or use it

You can take diphenhydramine tablets, capsules and liquid with or without food.

Always take your diphenhydramine tablets or capsules with a drink of water. Swallow them whole. Do not chew them.

Liquid medicines containing diphenhydramine come with a plastic syringe or spoon to help you measure out the right dose. If you do not have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as you will not get the right amount.

With the cream, put a small amount onto the affected area and smooth it in gently. Do not use it on large areas of skin. Keep the cream away from your eyes, mouth and nose. Remember to wash your hands afterwards - unless you're treating your hands.

What if I forget it?

If you're taking diphenhydramine to help you sleep and you forget to take it by bedtime, skip your missed dose and start again the next evening.

If you're taking any other medicine containing diphenhydramine and forget to take a dose, take your medicine when you next need it to ease your symptoms.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take or use too much?

Too much diphenhydramine can be dangerous.

If you've taken too much:

  • you may feel very sleepy or sick
  • your eyesight may be blurry
  • your heart may beat very fast

In serious cases you can become unconscious and may need emergency treatment in hospital.

Do not use diphenhydramine cream at the same time as other products containing diphenhydramine. This can lead to overdose.

Side effects

Like all medicines, diphenhydramine can cause side effects, although not everyone gets them. However, you may be more likely to get them if you're over 65.

Common side effects

Common side effects happen in more than 1 in 100 people. Talk to your doctor or pharmacist if these side effects bother you or do not go away:

  • feeling sleepy during the daytime
  • dry mouth
  • feeling dizzy or unsteady on your feet, or having difficulty concentrating

Diphenhydramine cream can sometimes make rashes worse. It may also make your skin sensitive to sunlight.

Serious side effects

Tell your doctor straight away if you:

  • have an irregular heartbeat
  • an increased awareness of your heartbeat
  • feel any numbness or pins and needles
  • feel confused or very restless
  • have had a fit or seizure – if someone around you is having a fit or seizure, call 999 straight away.

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to diphenhydramine.

These are not all the side effects of diphenhydramine. For a full list, see the leaflet inside your medicine packet.

How to cope with side effects

What to do about:

  • feeling sleepy during the daytime – drowsiness usually wears off 8 hours after a dose. Do not drive or use tools or machinery if you're feeling this way.
  • dry mouth – chew sugar-free gum or suck sugar-free sweets.
  • feeling dizzy or unsteady on your feet, or difficulty concentrating – if diphenhydramine makes you feel this way, 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 medicine and speak to a pharmacist or your doctor.

Pregnancy and breastfeeding

Diphenhydramine is not normally recommended during pregnancy.

This is because there is not enough information to be sure it's safe. If you take diphenhydramine towards the end of your pregnancy, there's a risk your baby may be born with some of the side effects.

If you have insomnia while you're pregnant, your doctor or midwife may suggest ways to improve your sleep routine - like relaxing, and avoiding naps. If this does not work, your doctor may prescribe a different antihistamine called promethazine to help you sleep.

If you have a cough or cold, you can help to ease your symptoms by resting, drinking plenty of fluids and taking everyday painkillers such as paracetamol.

Diphenhydramine and breastfeeding

Diphenhydramine is not normally recommended when breastfeeding, as small amounts of the medicine pass into your breast milk. It may also reduce the amount of milk you produce.

Talk to your doctor, as other medicines might be better while you're breastfeeding. It's usually safe to take similar antihistamines called loratadine and cetirizine while you're breastfeeding. If you need a drowsy antihistamine to help you sleep, your doctor may recommend chlorphenamine.

However, speak to your doctor before taking any antihistamine if your baby was premature, had a low birth weight or has health problems.

Cautions with other medicines

Some medicines and diphenhydramine interfere with each other and increase the chances of you having side effects. Check with your pharmacist or doctor if you're taking:

  • antidepressants, such as venlafaxine or a monoamine oxidase inhibitor such as phenelzine
  • metoprolol, a heart medicine
  • any medicine that makes you drowsy, gives you a dry mouth, or makes it difficult for you to pee – taking diphenhydramine might make these side effects worse

If you're taking a cough or cold remedy or a painkiller containing diphenhydramine, check carefully what the other ingredients are. For example, check whether it contains paracetamol. Ask your pharmacist for advice before you take this medicine together with any other painkillers or medicines.

Mixing diphenhydramine with herbal remedies and supplements

There might be a problem taking some herbal remedies and supplements alongside diphenhydramine – especially ones that cause side effects such as sleepiness, a dry mouth or make it difficult to pee.

Common questions

HealthUnlocked contains information from NHS Digital, licensed under the current version of the Open Government Licence

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32 public posts

Something to try if you suffer from the dreaded MPN itches

I tried 4 different antihistamines...hydroxyzine, diphenhydramine, allegra and fenfoxadine...they did absolutely nothing. I read that pepcid could help with hives because it is a H2 receptor antagonist.
I tried 4 different antihistamines...hydroxyzine, diphenhydramine, allegra and fenfoxadine...they did absolutely nothing. I read that pepcid could help with hives because it is a H2 receptor antagonist.
clubdino
in MPN Voice

Sciatica treatment

As Diphenhydramine contains an antihistamine I am not taking my usual antihistamine XYZAL which I take every day. I know I shouldn’t be surprised with all the combinations of drugs but I am getting very stressed. Thank you
As Diphenhydramine contains an antihistamine I am not taking my usual antihistamine XYZAL which I take every day. I know I shouldn’t be surprised with all the combinations of drugs but I am getting very stressed. Thank you
Bardsea
in IBS Network

Cycle 1 of Clinical Trials

Next I was given 650 mg of acetaminophen orally and 50 mg of diphenhydramine (Benadryl) IV which I hate the way that feels. Avelumab was infused 30 minutes later over an hour. I felt no side effects during the PT-112 infusion and a very small amount of itching during the avelumab infusion.
Next I was given 650 mg of acetaminophen orally and 50 mg of diphenhydramine (Benadryl) IV which I hate the way that feels. Avelumab was infused 30 minutes later over an hour. I felt no side effects during the PT-112 infusion and a very small amount of itching during the avelumab infusion.
Cleodman
in Advanced Prostate Cancer
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Sleeping struggle

I have little sleep each and every night and I had to take diphenhydramine every night that I developed dependence. I don’t feel rested at all and I don’t feel sleepy at night. Any thoughts on how to deal with this? Thanks
I have little sleep each and every night and I had to take diphenhydramine every night that I developed dependence. I don’t feel rested at all and I don’t feel sleepy at night. Any thoughts on how to deal with this? Thanks
sed3ntary
in Sleep Matters

Diphenhydramine/antihistamines shortened sleep-wake cycle?

I took 2 Benadryl tablets once 2 months ago to fall asleep earlier. That morning I woke up after only 6 hours of sleep (I usually get 8-9). Every day since then I've been getting only 6 hours of sleep per night, and I feel a strong urge to sleep in the afternoon (but I try not to). How do I reset my
I took 2 Benadryl tablets once 2 months ago to fall asleep earlier. That morning I woke up after only 6 hours of sleep (I usually get 8-9). Every day since then I've been getting only 6 hours of sleep per night, and I feel a strong urge to sleep in the afternoon (but I try not to). How do I reset my
billwright123
in Sleep Matters

Diphenhydramine

How long does it take for Diphenhydrami ne to leave the system as I want to try another sleep aid?
How long does it take for Diphenhydrami ne to leave the system as I want to try another sleep aid?
jonboy40
in Sleep Matters

Sominex

I live in the U.K. and Ive just bought a box of Sominex,which says it contains Promethazine HydrochloridePh.Eu.20mgs, surely this is not the same as Diphenhydramine?
I live in the U.K. and Ive just bought a box of Sominex,which says it contains Promethazine HydrochloridePh.Eu.20mgs, surely this is not the same as Diphenhydramine?
jonboy40
in Sleep Matters

Promethazine/Diphhydramine

Promethazine/Dipenhydramine Can I take Promethazine 2 or 3 nights after Diphenhydramine?
Promethazine/Dipenhydramine Can I take Promethazine 2 or 3 nights after Diphenhydramine?
jonboy40
in Mental Health Support

Amiodarone & Bisoprolol

This works well and better than Nytol one a night (Diphenhydramine) which if it any help gives me bad RLS.
This works well and better than Nytol one a night (Diphenhydramine) which if it any help gives me bad RLS.
Mike-tyson
in AF Association

Controlling Lesion Pain

That’s 100 ml of the Lidocaine & 60-80 ml of antacid (maalox) and Diphenhydramine HCI (Benadryl) ea. Mix and sip just enough to touch the lesions. Hold in mouth four 5 minutes. 1/4 teaspoon? I usually swallow since I have lesions down in my throat.
That’s 100 ml of the Lidocaine & 60-80 ml of antacid (maalox) and Diphenhydramine HCI (Benadryl) ea. Mix and sip just enough to touch the lesions. Hold in mouth four 5 minutes. 1/4 teaspoon? I usually swallow since I have lesions down in my throat.
Number4
in Behçet's UK

Antihistamines reversed tumor-enhancing effects of myeloid-derived suppressor cells

Antihistamines include H1 blockers (loratadine, diphenhydramine, etc,) for allergies treatment, and H2 blockers (Cimetidine, Ranitidine, etc,) for gastric ulcers, gastritis. Here is the finding (kind of old July 2014): To reach their findings, the team analyzed two groups of mice.
Antihistamines include H1 blockers (loratadine, diphenhydramine, etc,) for allergies treatment, and H2 blockers (Cimetidine, Ranitidine, etc,) for gastric ulcers, gastritis. Here is the finding (kind of old July 2014): To reach their findings, the team analyzed two groups of mice.
Ralph1966
in Advanced Prostate Cancer

I Gave up Cigs

I have even successfully taken 50mg of Diphenhydramine to help me sleep (oxymoron, huh?). I’m still on Mirapex and plan on going forward with that until something changes. I hope all are having a good day!!
I have even successfully taken 50mg of Diphenhydramine to help me sleep (oxymoron, huh?). I’m still on Mirapex and plan on going forward with that until something changes. I hope all are having a good day!!
LisztLover
in Restless Legs Syndrome

CT Scan with Iodine Contrast

The doctor has prescribed desamethasone (a steroid) for 8 hours and 4 hours before the infusion, and diphenhydramine HCl (Benedryl) 1 hour before. That should take care of the allergic reaction. But b) I have heard that large amounts of iodine can interfere with treatment for hypothyroidism.
The doctor has prescribed desamethasone (a steroid) for 8 hours and 4 hours before the infusion, and diphenhydramine HCl (Benedryl) 1 hour before. That should take care of the allergic reaction. But b) I have heard that large amounts of iodine can interfere with treatment for hypothyroidism.
vocalEK
in Thyroid UK

WHY AM I ON ALL THESE MEDS ?* I'M LIKE, "WOW" !* I JUST TURNED 61 & HAVE ALL THIS ?* WHEN MOST TESTS SAY NOTHING SERIOUS ?* BOTHERS ME !*

Xanax Oral > celecoxib Oral > tizanidine Oral > omeprazole Oral > Paxil Oral > Hyzaar Oral > bisoprolol fumarate Oral > nifedipine Oral > diphenhydramine oral & A FEW MORE !*.... This Is NUTS !*...In My Tests There's Been Nothing Really Serious To Cause Allot Of My Symptoms ? Yet ? Here We Are !
Xanax Oral > celecoxib Oral > tizanidine Oral > omeprazole Oral > Paxil Oral > Hyzaar Oral > bisoprolol fumarate Oral > nifedipine Oral > diphenhydramine oral & A FEW MORE !*.... This Is NUTS !*...In My Tests There's Been Nothing Really Serious To Cause Allot Of My Symptoms ? Yet ? Here We Are !
TriggerPoint
in Anxiety Support

Introduction

(With large enough doses of Diphenhydramine I could almost completely knock out the tremor. But the side effects weren’t worth it).
(With large enough doses of Diphenhydramine I could almost completely knock out the tremor. But the side effects weren’t worth it).
Georgeofthejungle
in Parkinson's Movement

ENDOSCOPY - SEDATION TO ANESTHESIA - GUIDANCE (USA protocols)

Diphenhydramine as an adjunct to sedation for colonoscopy: a double-blind randomized, placebocontrolled study. Gastrointest Endosc 2006;63:87-94. 50. Cohen LB, Hightower CD, Wood DA, et al.
Diphenhydramine as an adjunct to sedation for colonoscopy: a double-blind randomized, placebocontrolled study. Gastrointest Endosc 2006;63:87-94. 50. Cohen LB, Hightower CD, Wood DA, et al.
gutlesswonder
in Oesophageal Patients Association

First rodeo

Diphenhydramine inj. Hydrocortisone sod succinate inj. Methyprednisoolne sod succ, inj. Dosetaxel inj. and finally Palonosetron hcl,inj.
Diphenhydramine inj. Hydrocortisone sod succinate inj. Methyprednisoolne sod succ, inj. Dosetaxel inj. and finally Palonosetron hcl,inj.
bhr17
in Advanced Prostate Cancer

DYSPHAGIA - Medications that can cause Swallowing Problems

cardiac preparations – Disopyramide (Norpace), Mexiletine (Mexitil), Procainamide (Procan) Antiemetics; used for nausea – Meclizine (Antivert), Metoclopramide (Reglan), Prochlorperazine (Compazine) Antihistamines and decongestants; used for cold symptoms – Chlorpheniramine (Chlor-Trimeton), Diphenhydramine
cardiac preparations – Disopyramide (Norpace), Mexiletine (Mexitil), Procainamide (Procan) Antiemetics; used for nausea – Meclizine (Antivert), Metoclopramide (Reglan), Prochlorperazine (Compazine) Antihistamines and decongestants; used for cold symptoms – Chlorpheniramine (Chlor-Trimeton), Diphenhydramine
gutlesswonder
in Oesophageal Patients Association

Keep safe in the Sun

have an additive effect in causing sun sensitivity include: •Antibiotics, such as Cipro (ciprofloxacin), Levaquin (levofloxacin), tetracycline, doxycycline, and Septra or Bactrim (sulfamethoxazole-trimethoprim) •Diuretics, such as Lasix (furosemide) and Hydrodiuril (hydrochlorothiazide) •Benadryl (diphenhydramine
have an additive effect in causing sun sensitivity include: •Antibiotics, such as Cipro (ciprofloxacin), Levaquin (levofloxacin), tetracycline, doxycycline, and Septra or Bactrim (sulfamethoxazole-trimethoprim) •Diuretics, such as Lasix (furosemide) and Hydrodiuril (hydrochlorothiazide) •Benadryl (diphenhydramine
LCNurseLeukaemiaCARE Nurse
in Leukaemia CARE

Memory Loss & Prescription Drugs

Common prescriptions include: Amitriptyline (Elavil), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan), imipramine (Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil) and trimipramine (Surmontil) Antihistamines Common medications include: diphenhydramine (Benadryl),brompheniramine
Common prescriptions include: Amitriptyline (Elavil), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan), imipramine (Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil) and trimipramine (Surmontil) Antihistamines Common medications include: diphenhydramine (Benadryl),brompheniramine
ChristianElliottAdministrator
in Memory Health: Alzheimer's Support Group
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