Diphenhydramine

pronounced as (dye fen hye' dra meen)

Brand Name(s): Aler-Dryl®, Allergia-C®, Allermax®, Altaryl®, Banophen®, Ben Tann®, Benadryl®, Bromanate AF®, Compoz Nighttime Sleep Aid®, Dicopanol®, Diphedryl®, Diphen®, Diphenadryl®, Diphenhist®, Diphenylin®, Dytan®, Hydramine®, Nytol®, Pardryl®, PediaCare Children's Allergy®, Siladryl®, Silphen®, Sominex®, Unisom®, Advil PM® (as a combination product containing Diphenhydramine, Ibuprofen), Alahist LQ® (as a combination product containing Diphenhydramine, Phenylephrine), Aldex CT® (as a combination product containing Diphenhydramine, Phenylephrine), Aleve PM® (as a combination product containing Diphenhydramine, Naproxen), Anacin P.M. Aspirin Free®(as a combination product containing Acetaminophen, Diphenhydramine) ¶, Bayer Aspirin PM® (as a combination product containing Aspirin, Diphenhydramine), Benadryl-D Allergy Plus Sinus® (as a combination product containing Diphenhydramine, Phenylephrine), Children's Dimetapp Nighttime Cold and Congestion® (as a combination product containing Diphenhydramine, Phenylephrine), Doans PM®(as a combination product containing Diphenhydramine, Magnesium Salicylate) ¶, Endal HD®(as a combination product containing Diphenhydramine, Phenylephrine) §, Excedrin PM® (as a combination product containing Acetaminophen, Diphenhydramine), Goody's PM® (as a combination product containing Acetaminophen, Diphenhydramine), Legatrin PM® (as a combination product containing Acetaminophen, Diphenhydramine), Masophen PM®(as a combination product containing Acetaminophen, Diphenhydramine) ¶, Midol PM® (as a combination product containing Acetaminophen, Diphenhydramine), Motrin PM® (as a combination product containing Diphenhydramine, Ibuprofen), PediaCare Children's Allergy and Cold® (as a combination product containing Diphenhydramine, Phenylephrine), Robitussin Night Time Cough and Cold® (as a combination product containing Diphenhydramine, Phenylephrine), Sudafed PE Day/Night Cold® (as a combination product containing Acetaminophen, Dextromethorphan, Diphenhydramine, Guaifenesin, Phenylephrine), Sudafed PE Day/Night Congestion® (as a combination product containing Diphenhydramine, Phenylephrine), Sudafed PE Severe Cold® (as a combination product containing Acetaminophen, Diphenhydramine, Phenylephrine), Tekral®(as a combination product containing Diphenhydramine, Pseudoephedrine) §, Theraflu Nighttime Severe Cold and Cough® (as a combination product containing Acetaminophen, Diphenhydramine, Phenylephrine), Triaminic Night Time Cold and Cough® (as a combination product containing Diphenhydramine, Phenylephrine), Tylenol Allergy Multi-Symptom Nighttime® (as a combination product containing Acetaminophen, Diphenhydramine, Phenylephrine), Tylenol Severe Allergy® (as a combination product containing Acetaminophen, Diphenhydramine), Unisom with Pain Relief® (as a combination product containing Acetaminophen, Diphenhydramine), also available generically
Back to Drug Library

Why is this medicine prescribed?

Diphenhydramine is used to relieve red, irritated, itchy, watery eyes; sneezing; and runny nose caused by hay fever, allergies, or the common cold. Diphenhydramine is also used to relieve cough caused by minor throat or airway irritation. Diphenhydramine is also used to prevent and treat motion sickness, and to treat insomnia (difficulty falling asleep or staying asleep). Diphenhydramine is also used to control abnormal movements in people who have early stage parkinsonian syndrome (a disorder of the nervous system that causes difficulties with movement, muscle control, and balance) or who are experiencing movement problems as a side effect of a medication.

Diphenhydramine will relieve the symptoms of these conditions but will not treat the cause of the symptoms or speed recovery. Diphenhydramine should not be used to cause sleepiness in children. Diphenhydramine is in a class of medications called antihistamines. It works by blocking the action of histamine, a substance in the body that causes allergic symptoms.

Are there other uses for this medicine?

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

How should this medicine be used?

Diphenhydramine comes as a tablet, a rapidly disintegrating (dissolving) tablet, a capsule, a liquid-filled capsule, a dissolving strip, powder, and a liquid to take by mouth. When diphenhydramine is used for the relief of allergies, cold, and cough symptoms, it is usually taken every 4 to 6 hours. When diphenhydramine is used to treat motion sickness, it is usually taken 30 minutes before departure and, if needed, before meals and at bedtime. When diphenhydramine is used to treat insomnia it is taken at bedtime (30 minutes before planned sleep). When diphenhydramine is used to treat abnormal movements, it is usually taken three times a day at first and then taken 4 times a day. Follow the directions on the package or on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take diphenhydramine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor or directed on the label.

Diphenhydramine comes alone and in combination with pain relievers, fever reducers, and decongestants. Ask your doctor or pharmacist for advice on which product is best for your symptoms. Check nonprescription cough and cold product labels carefully before using two or more products at the same time. These products may contain the same active ingredient(s) and taking them together could cause you to receive an overdose. This is especially important if you will be giving cough and cold medications to a child.

Nonprescription cough and cold combination products, including products that contain diphenhydramine, can cause serious side effects or death in young children. Do not give these products to children younger than 4 years of age. If you give these products to children 4 to 11 years of age, use caution and follow the package directions carefully.

If you are giving diphenhydramine or a combination product that contains diphenhydramine to a child, read the package label carefully to be sure that it is the right product for a child of that age. Do not give diphenhydramine products that are made for adults to children.

Before you give a diphenhydramine product to a child, check the package label to find out how much medication the child should receive. Give the dose that matches the child's age on the chart. Ask the child's doctor if you don't know how much medication to give the child.

If you are taking the liquid, do not use a household spoon to measure your dose. Use the measuring spoon or cup that came with the medication or use a spoon made especially for measuring medication.

If you are taking the dissolving strips, place the strips on your tongue one at a time and swallow after they melt.

If you are taking the rapidly dissolving tablets, place a tablet on your tongue and close your mouth. The tablet will quickly dissolve and can be swallowed with or without water.

If you are taking the capsules, swallow them whole. Do not try to break the capsules.

What special precautions should I follow?

Before taking diphenhydramine,

  • tell your doctor and pharmacist if you are allergic to diphenhydramine, any other medications, or any of the ingredients in diphenhydramine preparations. Ask your doctor or pharmacist or check the package label for a list of the ingredients.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take while taking diphenhydramine.Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you have or have ever had asthma, emphysema, chronic bronchitis, or other types of lung disease; glaucoma (a condition in which increased pressure in the eye can lead to gradual loss of vision); ulcers; difficulty urinating (due to an enlarged prostate gland); heart disease; high blood pressure; seizures; or an overactive thyroid gland.If you will be using the liquid, tell your doctor if you have been told to follow a low-sodium diet.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking diphenhydramine, call your doctor.
  • you should know that this medication may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.
  • you should know that generally diphenhydramine should not be used in older adults, except to manage serious allergic reactions, because it is not as safe or effective as other medication(s) to treat your condition. If you are 65 years of age or older, talk to your doctor about the risks and benefits of taking this medication.
  • if you have phenylketonuria (PKU, an inherited condition in which a special diet must be followed to prevent damage to your brain that can cause severe intellectual disability), you should know that some brands of chewable tablets and rapidly disintegrating tablets that contain diphenhydramine may be sweetened with aspartame, a source of phenylalanine.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking diphenhydramine.
  • remember that alcohol can add to the drowsiness caused by this medication. Avoid alcoholic beverages while you are taking this medication.

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do if I forget to take a dose?

Diphenhydramine is usually taken as needed. If your doctor has told you to take diphenhydramine regularly, take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What should I do in case of overdose?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help . If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

What side effects can this medicine cause?

Diphenhydramine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • dry mouth, nose, and throat
  • drowsiness
  • dizziness
  • nausea
  • vomiting
  • loss of appetite
  • constipation
  • increased chest congestion
  • headache
  • muscle weakness
  • excitement (especially in children)
  • nervousness

Some side effects may be serious. If you experience any of the following symptoms, call your doctor immediately:

  • vision problems
  • difficulty urinating or painful urination

Diphenhydramine may cause other side effects. Call your doctor if you experience any unusual problems while you are taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( https://www.fda.gov/Safety/MedWatch ) or by phone (1-800-332-1088).

What should I know about storage and disposal of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location – one that is up and away and out of their sight and reach. https://www.upandaway.org

Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website https://goo.gl/c4Rm4p for more information.

What other information should I know?

Ask your pharmacist any questions you have about diphenhydramine.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

¶ This branded product is no longer on the market. Generic alternatives may be available.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS ® Patient Medication Information™. © Copyright, 2025. The American Society of Health-System Pharmacists ® , 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: January 15, 2022.