Skip to main content


Generic name: diphenhydramine (DYE fen HYE dra meen)
Brand name: Allermax, Benadryl, Compoz Nighttime Sleep Aid, Diphedryl, Dytuss, Nytol QuickCaps, Scot-Tussin Allergy Relief Formula, Siladryl Allergy, Simply Sleep, Sleepinal, Sominex, Twilite, Unisom Sleep Gels, Valu-Dryl, Vanamine PD, Z-Sleep, ZzzQuil
Drug class: Anticholinergic antiemetics, Anticholinergic antiparkinson agents, Antihistamines, Miscellaneous anxiolytics, sedatives and hypnotics

Medically reviewed by on Sep 29, 2020. Written by Cerner Multum.

What is Diphedryl?

Diphedryl is an antihistamine that is used to treat sneezing, runny nose, watery eyes, hives, skin rash, itching, and other cold or allergy symptoms.

Diphedryl is also used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson's disease. This medicine sleep aid medicine is not for use in children younger than 12 years old.

There are many brands and forms of diphenhydramine available. Not all brands are listed on this leaflet.

Diphedryl may also be used for purposes not listed in this medication guide.


Use Diphedryl exactly as directed. Taking too much Diphedryl can lead to serious heart problems, seizures, coma, or death.

Do not use this medicine to make a child sleepy. Diphedryl sleep aid medicine is not for use in children younger than 12 years old.

Before taking this medicine

You should not use Diphedryl if you are allergic to it.

Ask a doctor or pharmacist if this medicine is safe to use if you have ever had:

Ask a doctor before using this medicine if you are pregnant or breastfeeding. Diphedryl may slow breast milk production.

How should I take Diphedryl?

Use exactly as directed on the label, or as prescribed by your doctor. Diphedryl is only for short-term use until your symptoms clear up.

Taking too much Diphedryl can lead to serious heart problems, seizures, coma, or death.

Always follow directions on the medicine label about giving Diphedryl to a child. Do not use the medicine only to make a child sleepy. Death can occur from the misuse of antihistamines in very young children.

For motion sickness, take Diphedryl 30 minutes before you will be in a situation that causes you motion sickness (such as a long car ride, airplane or boat travel, amusement park rides, etc). Continue taking this medicine with meals and at bedtime for the rest of the time you will be in a motion-sickness situation.

As a sleep aid, take Diphedryl within 30 minutes before bedtime.

You must chew the chewable tablet before you swallow it.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Remove an orally disintegrating tablet from the package only when you are ready to take the medicine. Place the tablet in your mouth and allow it to dissolve, without chewing. Swallow several times as the tablet dissolves.

Call your doctor if the condition you are treating with Diphedryl does not improve, or if you have a fever with a headache, cough, or skin rash.

Do not use Diphedryl for longer than 2 weeks to treat sleep problems, or longer than 7 days to treat cold or allergy symptoms.

Diphedryl can affect the results of allergy skin tests. Tell any doctor who treats you that you are using Diphedryl.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Since Diphedryl is used when needed, you may not be on a dosing schedule. Skip any missed dose if it's almost time for your next dose. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of diphenhydramine can be fatal.

Overdose symptoms may include vomiting, confusion, severe drowsiness, ringing in your ears, no urination, very dry eyes and mouth, dilated pupils, fast heartbeats, tremor, agitation, hallucinations, or seizure.

What should I avoid while taking Diphedryl?

Avoid driving or hazardous activity until you know how Diphedryl will affect you. Your reactions could be impaired.

Drinking alcohol can increase certain side effects of diphenhydramine.

Ask a doctor or pharmacist before using any other medicine that may contain Diphedryl. This includes medicines for sleep, cold/allergy symptoms, or anti-itch medicine used on the skin. Using too much this medicine may lead to a fatal overdose.

Diphedryl side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using Diphedryl and call your doctor at once if you have:

  • severe drowsiness; or

  • painful or difficult urination.

Side effects such as dry mouth, constipation, and confusion may be more likely in older adults.

Common side effects may include:

  • drowsiness;

  • dry eyes, blurred vision;

  • dry mouth, nose, or throat;

  • decreased urination;

  • constipation;

  • feeling restless or excited (especially in children); or

  • day-time drowsiness or "hangover" feeling after night-time use.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Diphedryl?

Ask a doctor or pharmacist before using Diphedryl with any other medicines, especially drugs that can cause drowsiness (such as opioid medication, sleep medicine, a muscle relaxer, or medicine for anxiety or seizures). Tell your doctor about all your current medicines and any medicine you start or stop using. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here.

Does Diphedryl interact with my other drugs?

Enter other medications to view a detailed report.

Frequently asked questions

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.