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Benadryl

Generic name: diphenhydramine

Used for allergy symptoms
Last updated August 14, 2026 0 views Reviewed by Sanjai Sinha, MD
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What is Benadryl?

Benadryl is an antihistamine that reduces the effects of natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose.

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

Benadryl is also used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson's disease.

How should I take Benadryl?

Use Benadryl exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Cold or allergy medicine is usually taken only for a short time until your symptoms clear up.

Do not give this medication to a child younger than 2 years old. Always ask a doctor before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children.

You should not use Benadryl to make a child sleepy.

Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

For motion sickness, take Benadryl 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 Benadryl with meals and at bedtime for the rest of the time you will be in a motion-sickness situation.

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

Call your doctor if your symptoms do not improve after 7 days of treatment, or if you have a fever with a headache, cough, or skin rash.

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

Store at room temperature away from moisture and heat.

Warnings

You should not use Benadryl to make a child sleepy.

When taking Benadryl, use caution driving, operating machinery, or performing other hazardous activities. Diphenhydramine may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities.

Use alcohol cautiously. Alcohol may increase drowsiness and dizziness while taking Benadryl.

Do not give this medication to a child younger than 2 years old. Always ask a doctor before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children.

Before taking this medicine

You should not use Benadryl if you are allergic to diphenhydramine.

Ask a doctor or pharmacist if it is safe for you to take this medicine if you have other medical conditions, especially:

  • blockage in your digestive tract (stomach or intestines);
  • bladder obstruction or other urination problems;
  • a colostomy or ileostomy;
  • liver or kidney disease;
  • asthma, chronic obstructive pulmonary disease (COPD), or other breathing disorder;
  • cough with mucus, or cough caused by smoking, emphysema, or chronic bronchitis;
  • heart disease, low blood pressure;
  • glaucoma;
  • a thyroid disorder; or
  • if you take potassium (Cytra, Epiklor, K-Lyte, K-Phos, Kaon, Klor-Con, Polycitra, Urocit-K).

It is not known whether Benadryl will harm an unborn baby. Ask a doctor before using this medicine if you are pregnant.

Diphenhydramine can pass into breast milk and may harm a nursing baby. Antihistamines may also slow breast milk production. Ask a doctor before using this medicine if you are breast-feeding.

Older adults may be more likely to have side effects from this medicine.

Benadryl side effects

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

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

  • pounding heartbeats or fluttering in your chest;
  • painful or difficult urination;
  • little or no urinating;
  • confusion, feeling like you might pass out; or
  • tightness in your neck or jaw, uncontrollable movements of your tongue.

Common Benadryl side effects may include:

  • dizziness, drowsiness, loss of coordination;
  • dry mouth, nose, or throat;
  • constipation, upset stomach;
  • dry eyes, blurred vision; or
  • day-time drowsiness or "hangover" feeling after night-time use.
  • excitability, especially in children.

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 happens if I miss a dose?

Since Benadryl is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Benadryl may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

Drinking alcohol can increase certain side effects of diphenhydramine.

Do not use Benadryl with any other product containing diphenhydramine, even one used on the skin. Ask a doctor or pharmacist before using any other cold, cough, allergy, or sleep medicine. Antihistamines are contained in many combination medicines. Taking certain products together can cause you to get too much of this type of medicine. Check the label to see if a medicine contains an antihistamine.

What other drugs will affect Benadryl?

Ask a doctor or pharmacist before using this medicine if you are also using any other drugs, including prescription and over-the-counter medicines, vitamins, and herbal products. Some medicines can cause unwanted or dangerous effects when used together. Not all possible interactions are listed in this medication guide.

Taking this medicine with other drugs that make you sleepy or slow your breathing can worsen these effects. Ask your doctor before taking Benadryl with a sleeping pill, narcotic pain medicine, muscle relaxer, or medicine for anxiety, depression, or seizures. Tell your doctor or pharmacist if you are taking an MAO inhibitor, as it can increase the drying effects of Benadryl.

Common questions about Benadryl

Can you take Benadryl and cetirizine together?
Benadryl should not be taken at the same time as cetirizine because it can increase side effects such as dizziness, drowsiness, and difficulty concentrating. Some people, especially the elderly or children, may also find their thinking, judgement, and coordination impaired. You should also not drink alcohol while taking either of these medications because it can make these side effects worse.
What is the max dose of diphenhydramine for adults?
The maximum oral dose of diphenhydramine for adults is generally reported as 50 to 100 mg for a single dose or no more than 300 mg in 24 hours, but this can vary depending on what condition diphenhydramine is being used for, the salt of diphenhydramine used (there are two salts available in the US diphenhydramine citrate and diphenhydramine chloride), the age of the person, how much diphenhydramine they have tolerated before, and if they are on any interacting medications. Taking too much diphenhydramine can be fatal. Continue reading
How much Benadryl can I take? What is too much?
The maximum safe Benadryl (diphenhydramine) dose for adults is 50 to 100 mg for a single dose with a daily maximum of 300 mg in 24 hours. However, your safe Benadryl dose depends on your medical conditions, age, previous tolerance to diphenhydramine, other medications you take, weight and body size, what condition you are using Benadryl for. Continue reading
What is the Benadryl hat man?
The Hat Man is a fictional figure that started appearing on certain internet sites in the early 2000s that has recently been referred to as the “Benadryl Hat Man” after reports of people hallucinating and sighting him after overconsumption or abuse of Benadryl. Most of these reports have appeared on Reddit or the image-based bulletin site 4chan. Continue reading
Which antihistamines are safe for dogs?
According to the American Kennel Club (AKC), you can give the antihistamine Benadryl (diphenhydramine) to your dog, but you should always check with your vet first. Continue reading
What cold medicine can you take with diabetes?
If you have diabetes and you catch a cold or flu, there are over-the-counter (OTC) medicines that are safe for you to take to help alleviate your symptoms. Check out our suggestions for pain and fever relievers, cough and congestion medications and more. Remember to look for cold and flu medicines that are less likely to affect your blood sugar (glucose) levels, including sugar-free and alcohol-free options, or worsen any diabetes complications you may have. Continue reading
Can you take Benadryl and Zyrtec together? Why it's not advised?
You should not take Benadryl and Zyrtec together unless directed by your doctor. Both are antihistamines, and combining them can increase risks for drowsiness, confusion, and other side effects. Continue reading
How Fast Does Benadryl Work? Onset Time and Duration
Benadryl starts working within 30 minutes after taking it orally, with peak effects reached in 1-2 hours. The antihistamine effects last 4-6 hours for most people. Injectable Benadryl works even faster than oral tablets, providing quicker relief for severe allergic reactions. Continue reading
Does Benadryl make you sleepy?
Benadryl (diphenhydramine) is a first‑generation antihistamine that often makes you sleepy for around 8 hours. It can also cause confusion, falls, or ‘paradoxical’ agitation, so it’s not recommended as a regular sleep aid, especially in children and older adults. Continue reading

Related medicines

Before you take this medicine: the information on this page is general and may not cover your personal circumstances. Read the label supplied with your medicine and ask a pharmacist or doctor if you are unsure, especially if you are pregnant, breastfeeding, taking other medicines or managing a long-term condition.
General medicine information Consumer-friendly language Source: Drugs.com

Content is provided for education and is not medical advice. See our medical disclaimer. Source page medically reviewed by Sanjai Sinha, MD on August 14, 2026.