What to Know About Benadryl (Diphenhydramine)

Benadryl (diphenhydramine) is a popular antihistamine drug that can be purchased over the counter (OTC). Benadryl comes in oral tablet, chewable tablet, liquid-filled capsule, and liquid solution forms for the treatment of mild symptoms of the common cold or allergies, including a runny nose, sneezing, and itching. There are also topical forms of Benadryl (anti-itch creams, gels, and sprays) that may be applied to irritated skin.

The medication works by blocking the effects of histamine, a substance released by the body as an immune response. Histamines plays a major role in nasal allergy symptoms, such as mucus, swelling, and itching.

Other OTC diphenhydramine brands include Aler-Dryl (tablets), PediaCare Children's Allergy (oral solution), and Silphen (oral solution). Diphenhydramine is also available in generic formulations.

Uses

Oral forms of Benadryl are approved to address mild symptoms of indoor or outdoor allergies, such as hay fever, or the common cold in adults and children ages 6 and older.

Oral forms of the medication can help improve:

• Runny nose
• Sneezing
• Itchy or watery eyes
• Itchy throat (from allergies and minor throat irritation)
• Acute skin reactions, such as urticaria (hives)
• Motion sickness

Topical Benadryl can be used as an analgesic to soothe itchy and irritated skin in adults and children over age 2. When applied to skin, the medication reduces itch and also acts as an analgesic to temporarily ease pain, such as from insect bites, rashes, poison ivy, or sunburns.

All forms of Benadryl are also considered anticholinergic drugs since they can block activity of the neurotransmitter acetylcholine, which transmits messages within the brain and throughout the central nervous system.

Off-Label Uses

Benadryl is sometimes used as an off-label treatment for insomnia since drowsiness is a common side effect. (OTC sleep aids such as Unisom and Nytol contain diphenhydramine for this reason.)

It's also used off-label for oral mucositis, a swelling of the mouth, or as a local anesthetic for people who are allergic to other types of local anesthetics.

Before Taking

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

If it's possible for you to avoid or address the allergens through environmental interventions, such as mold remediation or pest control, you may be able to eliminate or reduce symptoms without the use of medications (or at least reduce how often you need to take them).

If that's not sufficient, or if your symptoms are severe, your doctor will likely try you on a second-generation antihistamine for allergies or skin reactions. Options include:

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

Compared to first-generation options like diphenhydramine, these newer drugs have fewer side effects because they more directly target histamine receptors. And unlike their predecessors, second-generation antihistamines are not anticholinergics, so they do not carry additional risks for certain individuals that Benadryl does (see below).

Despite these options being preferred because of their side effect and risk profile, your doctor may still recommend Benadryl as an alternative antihistamine option if:

• You are using it as a short-term treatment for allergies or skin irritations
• You've used it with success previously
• Other drug options are cost-prohibitive

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

Precautions and Contraindications

As an anticholinergic drug, Benadryl may worsen certain conditions or lead to serious complications.

Talk with your doctor before taking Benadryl if you have any of the following conditions that can make taking Benadryl risky or prohibit its use:

• Emphysema, chronic bronchitis, or other breathing problems
• Benign prostatic hypertrophy (enlarged prostate)
• Glaucoma
• Heart disease
• Hypertension (high blood pressure)
• Hyperthyroidism
• Epilepsy
• Gastrointestinal obstructive disorders
• Urinary obstruction
• Risk factors for dementia or Alzheimer's disease

Research has found 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 Alzheimers or dementia or if you plan to take Benadryl frequently. Your may want to switch to a second-generation antihistamines that 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:

• Allergy or hypersensitivity: Do not take Benadryl if you have a known allergy or hypersensitivity to it or other types of antihistamines. If you are allergic or sensitive to gelatin, do not take the liqui-gel capsules.
• Pregnancy: While studies suggest that taking antihistamines during pregnancy is not linked to birth defects, there is a lack of adequate and well-controlled human studies and more research is needed. Your doctor can help you evaluate whether you should limit or avoid Benadryl while pregnant.
• Nursing: Antihistamines can be transferred to the infant in breastmilk and are typically not recommended while breastfeeding.
• People ages 65 and older: Elderly patients are more likely to have impaired liver or kidney function and are more at risk of dementia or falling when drowsy, so they may need to be evaluated or take a second-generation antihistamine instead of Benadryl.

Other Treatment Options

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

• Ala-Hist IR (dexbrompheniramine)
• Chlor-Trimeton, Aller-Chlor (chlorpheniramine)
• Tavist, Dayhist Allergy (clemastine)

Vistaril (hydroxyzine) is a prescription first-generation antihistamine that is prescribed for itchy skin due to chronic hives or skin reactions or anxiety.

If antihistamines of any kind are not effective in managing allergies or hives or you are unable to tolerate or take them, your doctor may have you try other types of allergy medications, such as Singulair (montelukast) that targets molecules called leukotrienes that contribute to mucus and inflammation, or Xolair (omalizumab) that targets immunoglobulin E (IgE) antibodies in the bloodstream that are responsible for an allergic response.

Another more long-term option is immunotherapy (allergy shots or tablets), which exposes you to small amounts of the allergens to desensitize your body to them over time.

Dosage

Benadryl is short-acting and taken every four to six hours with no more than six doses taken within 24 hours. It comes in 25-milligram (mg) tablets, 25-mg liquid-filled gel capsules, 12.5-mg chewable tablets, and 12.5-mg doses taken as a liquid solution, which is 12.5 mg per teaspoon/5 milliliters (mL).

The standard dosages of oral Benadryl are as follows:

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

Topical Benadryl can be applied as a thin coat to skin up to four times a day and for no longer than seven days.

Modifications

Your doctor may recommend a lower starting dose of Benadryl if you have liver or kidney impairment since you may not clear antihistamines as efficiently, which puts you at a greater risk of toxicity.

How to Take and Store

Benadryl can be taken with or without food. The drug usually starts to work within an hour.

Store is at room temperature that's ideally 68 to 77 degrees F for tablets and liquid solution and 59 to 77 degrees F for capsules. Protect the medication by keeping it out of heat and direct light. As with all medications, keep it out of reach of children.

If you take more than the recommended dose or have any signs of overdose, such as severe sedation or blurry vision, seek urgent medical care.

If a topical Benadryl is swallowed, seek urgent medical care or call poison control.

Side Effects

Benadryl is typically well tolerated, but does carry the risk of serious side effects.

Common

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

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

Severe

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

• Changes in vision
• Confusion
• Extreme nervousness
• Racing heartbeat
• Nausea or vomiting
• Stomach pain
• Lack of urination or difficult or painful urination
• Painful urination
• Yellowing of skin
• Weakness
• Difficulty breathing
• Swelling of the face, mouth, tongue, or throat

Warnings and Interactions

Benadryl can impair your ability to function and should never be used if you are planning to drive. Many state laws will charge you with a DUI (driving under the influence) if you are deemed to have been impaired by Benadryl.

You should never drink alcohol when taking Benadryl as this can only enhance side effects like drowsiness and decreased alertness, and become dangerous or life-threatening. The same applies to any other central nervous system (CNS) depressants, such as tranquilizers, hypnotics (sleeping pills), pain medications, or sedatives.

Always consult your doctor before taking Benadryl along with other medications due the risk of interactions.

You should not use any topical cream containing diphenhydramine if you have chickenpox, measles, broken skin, or large areas of skin that need to be treated.

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