What you need to know about Benadryl (diphenhydramine)


Benadryl ( diphenhydramine ) is an antihistamine used to treat mild symptoms of a cold or allergy , including a runny nose, sneezing, and itching. It is available over the counter (OTC) and comes in the form of oral tablets, chewable tablets, liquid-filled capsules, and liquid solutions. Topical anti-itch creams, gels, and sprays containing Benadryl are used to treat certain types of skin irritation.

The medicine works by blocking the action of histamine , a substance released by the body as part of the immune response. Histamines play an important role in mediating nasal allergy symptoms, such as excessive mucus production, edema, and itching .

Other over-the-counter brands of diphenhydramine include Aler-Dryl (tablets), PediaCare Children's Allergy (oral solution), and Silphen (oral solution). Diphenhydramine is also available in generic form.


Oral Benadryl is approved for the treatment of mild allergies, hay fever , or cold symptoms in adults and children 6 years of age and older.

Oral forms of the drug can help improve:

  • Runny nose
  • Sneezing
  • Itchy or watery eyes
  • Itchy throat (from allergies and mild throat irritation)
  • Acute skin reactions such as hives (hives).
  • Dizziness

Benadryl topical can be used to soothe irritated and itchy skin in adults and children over 2 years of age. When applied to the skin, the drug reduces itching and temporarily relieves pain, such as from insect bites, rashes, poison ivy , or sunburn.

All forms of Benadryl are also considered anticholinergic drugs because they can decrease the activity of the neurotransmitter acetylcholine, which transmits messages to the brain and the entire central nervous system.

Use not indicated on the label

Benadryl is sometimes used incorrectly for insomnia because drowsiness is a common side effect. (For this reason, over-the-counter sleeping pills like Unisom and Nytol contain diphenhydramine.)

It is also used off-label for oral mucositis, a type of swelling in the mouth .

Before drinking

If you have year-round or seasonal allergy symptoms , your healthcare provider may perform a blood or skin test to confirm and determine your allergy. Common allergens include pollen, mold, dust mites, pets (dogs, cats), and pests (cockroaches, mice).

If you can prevent allergens from occurring through environmental measures such as mold removal or pest control, you can eliminate or reduce symptoms without using medications (or at least reduce the frequency of taking them).

If that's not enough, or if you have severe symptoms, your healthcare provider will most likely ask you to try second-generation antihistamines for allergies or skin reactions.

The options include:

  • Allegra (fexofenadine)
  • Clarinex (desloratadine)
  • Claritin (loratadine)
  • Ksizal (levocetirizine)
  • Zyrtec (cetirizine)

Compared to first-generation drugs like diphenhydramine, these newer drugs have fewer side effects, as they target histamine receptors more directly. And unlike their predecessors, second-generation antihistamines are not anticholinergic, so they do not carry the risks associated with anticholinergic activity, such as Benadryl.

Although these options are preferred due to their side effects and risk profile, your healthcare provider may recommend Benadryl as an alternative antihistamine if:

  • He uses it as a short-term treatment for allergies or skin irritations.
  • You have used this successfully before
  • Other drug options are not available at cost

There is no cure for a cold and Benadryl does not shorten the duration of a cold, but it can be taken for nasal and eye symptoms.

Talk to your doctor about all the medications, supplements, and vitamins that you are currently taking. While some medications carry little risk of interactions, others may directly contraindicate their use or cause careful consideration of whether the benefits of treatment outweigh the disadvantages in your case.

Precautions and contraindications.

As an anticholinergic drug, Benadryl can make certain conditions worse or cause serious complications.

Talk to your doctor before taking Benadryl if you have any of the following conditions that could make it risky or prevent you from taking Benadryl:

Studies have shown a link between anticholinergics, including first-generation antihistamines, and an increased risk of dementia and Alzheimer's disease. Tell your doctor if you have a family history of Alzheimer's or dementia or plan to take Benadryl frequently. You may want to switch to second generation antihistamines, which are not known to have this link.

There are also medical conditions that can make taking antihistamines risky or even prohibit their use. This includes:

  • Allergies or hypersensitivity: Do not take Benadryl if you are allergic or hypersensitive to this or other types of antihistamines. If you are allergic or sensitive to gelatin, do not take the liquid softgels.
  • Pregnancy: Although research shows that taking antihistamines during pregnancy is not associated with birth defects, adequate and well-controlled human studies are insufficient and more research is needed. Your healthcare provider can help you evaluate whether to limit or avoid taking Benadryl during pregnancy.
  • Diet: Antihistamines can be passed to the baby through breast milk and are generally not recommended during breastfeeding.
  • People 65 and older: Older patients are more likely to have liver or kidney problems and are at higher risk of dementia or falling asleep, so they may need to get tested or take second-generation antihistamines instead of Benadryl .

Combination products

Benadryl Allergy Plus Congestion and Children's Benadryl Allergy Plus Congestion Tablets are combination products with diphenhydramine and the decongestant phenylephrine. Do not take these medications if you are allergic to phenylephrine or if you have taken a monoamine oxidase inhibitor (MAOI) in the past two weeks. Phenylephrine can also be dangerous for people with certain medical conditions, such as diabetes , so always check with your doctor before taking a combination product.

Decongestants should not be taken for more than a few days in a row; when taken for a long time, paradoxically, they can cause a worsening of nasal symptoms.

Other treatment options

In addition to diphenhydramine, other first-generation over-the-counter antihistamines used for allergies and cold symptoms include:

  • Ala-Hist IR (dexbrompheniramine)
  • Chlor-Trimeton, Aller-Chlorine (chlorpheniramine)
  • Tavist, daytime allergy (clemastine)

Vistaril ( hydroxyzine ) is a first-generation prescription antihistamine that is prescribed for itching caused by chronic hives, skin reactions, or anxiety.

If antihistamines of any kind are ineffective at treating allergies or hives, or if you cannot tolerate or take them, your healthcare provider may ask you to try other types of allergy medications, such as Singulair (montelukast), which target molecules called leukotrienes that promote mucus development and inflammation. For chronic antihistamine-resistant hives, allergists may also prescribe Xolair (omalizumab) injections, which target immunoglobulin E (IgE) antibodies.

Another longer-term option is immunotherapy (allergy shots or pills), in which you are exposed to small amounts of allergens, allowing your body to pass them on over time.


Benadryl is short-acting and is taken every four to six hours, but no more than six doses in a 24-hour period. It comes in 25 milligram (mg) tablets, 25 mg softgels, 12.5 mg chewable tablets, and 12.5 mg doses as a liquid solution, which is 12.5 mg per teaspoon / 5 milliliters (ml).

Standard doses of oral Benadryl are as follows :

Age group Dose Maximum. Dose in 24 hours
adults and kids older than 12 years old 25   mg to 50 mg every four to six hours as needed 6
Children from 6 to 12 years old 12.5 mg (one chewable tablet) to 25 mg (one adult tablet) every four to six hours 6

Do not give oral Benadryl to children under 6 years of age unless directed by a pediatrician.

Topical Benadryl can be applied in a thin layer to the skin up to four times a day and no more than seven days.


Your healthcare professional may recommend a lower starting dose of Benadryl if you have liver or kidney problems because you cannot get rid of antihistamines effectively, increasing your risk of toxicity.

How to take and store

Benadryl can be taken with or without food. Usually the medicine begins to work within an hour.

Store the tablets and liquid solution at room temperature, ideally between 68 and 77 degrees Fahrenheit. Store the capsules between 59 and 77 degrees Fahrenheit, away from heat and direct light. As with all medicines, keep it out of the reach of children.

If you have taken more than the recommended dose or have any signs of an overdose, such as severe sedation or blurred vision, seek emergency medical attention.

If Benadryl topical is ingested, seek emergency medical attention or call a poison control center.

Side effects

Benadryl is generally well tolerated, but carries the risk of serious side effects.


Most side effects are mild and usually go away within a few hours. Common side effects include:

  • Drowsiness
  • Dizziness
  • Dry mouth, nose and throat.
  • Hoarseness
  • Headache
  • Excitability, mainly in children
  • Loss of appetite
  • Increased chest congestion
  • Constipation

Severe form

If you experience any of the following side effects while taking Benadryl, seek emergency medical attention:

  • Vision changes
  • Confusion
  • Extreme nervousness
  • Cardiopalmus
  • Nausea or vomiting
  • Abdominal pain
  • Lack of urination or difficulty or pain when urinating
  • Pain when urinating
  • Yellowing of the skin
  • Soft spot
  • Difficulty breathing
  • Swelling of the face, mouth, tongue, or throat

Warnings and interactions

Benadryl can affect your ability to function and should never be used if you plan to drive. Many state laws charge you for a DUI (driving under the influence) if you think Benadryl has harmed you.

You should never consume alcohol while taking Benadryl as it can aggravate side effects such as drowsiness and decreased activity and become life threatening or dangerous. The same applies to any other central nervous system (CNS) depressant , such as tranquilizers, hypnotics (sleeping pills), pain relievers , or sedatives.

Always check with your doctor before taking Benadryl with other medications due to the risk of interactions.

You should not use topical creams containing diphenhydramine if you have chickenpox, measles, damaged skin, or large areas of skin that require treatment.

Do not take two diphenhydramine medications at the same time, even if one is oral and the other is topical, due to the increased risk of side effects.

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