Why Trust Recovery Guide Benadryl is the brand name for diphenhydramine, an over-the-counter antihistamine that people commonly use to treat allergic reactions and seasonal allergy symptoms. It comes in pills, gels, and liquid forms that are widely available at pharmacies and stores.
When taken as directed, Benadryl’s effects typically last four to six hours, similar to other over-the-counter medications. The drug can remain in your system for two to three days after your last dose. While Benadryl is safe when used properly, some people abuse it by taking high doses to experience euphoria and hallucinations, which can be very dangerous.
So while Benadryl addiction is rare, these effects can make Benadryl abuse a risk for physical dependence and drug addiction.
How Long Does Benadryl (Diphenhydramine) Last?
As a first-generation antihistamine, Benadryl is a short-acting medication. It takes roughly 30 minutes to begin blocking histamine reactions in most people, and the effects usually last for four to six hours.
Other side effects may include:
- drowsiness and sedation
- constipation
- dry mouth
- dizziness
- nausea and vomiting
- muscle weakness
- excitability and nervousness
- hyperactivity, especially in pediatric patients
- headache
- blurred vision
- changes in heart rate
Therapeutic effects include relief from itching, sneezing, runny nose, hay fever, hives, and other allergy symptoms. Due to its sedative effects, some people misuse this medication as a sleep aid.
How Long Does Benadryl Last During A High?
There is very little research available on how long Benadryl lasts during a high compared to how long its therapeutic effects last. Anecdotally, people who have experienced a Benadryl high have described effects that lasted for several hours or even overnight.
However, Benadryl hallucinations can distort people’s perceptions of time, so anecdotal descriptions may not provide reliable information.
What Does A Benadryl High Feel Like?
A high from Benadryl often causes psychosis. People have described intense hallucinations that produce anxiety and sleep disturbances. Unlike psychedelic drugs, Benadryl rarely, if ever, produces a pleasant high.
In fact, some researchers believe that Benadryl has a low risk for addiction because people do not want to repeat the experience.
How Long Does Benadryl Last In The Body?
Research on Benadryl toxicity states that the half-life of Benadryl does not seem to change whether a person ingests therapeutic amounts or toxic amounts of the drug. For most healthy adults, Benadryl has a half-life of seven to 12 hours, with an average of nine hours.
Most medications, including Benadryl, take five to six half-lives to leave the body, so Benadryl may be present in the body for two to three days.
How Long Can Benadryl Be Detected By Drug Tests?
There’s limited information about how long Benadryl can be detected in drug tests because standard drug screenings aren’t designed to look for diphenhydramine or its breakdown products. Most routine workplace or medical drug tests don’t include Benadryl as a substance they’re checking for.
However, research shows that Benadryl can sometimes cause false positive results for other drugs on urine tests. This can happen for up to four days after taking Benadryl, with false positives most commonly showing up as methadone. If you’re facing a drug test and have taken Benadryl recently, it’s important to inform the testing facility beforehand to avoid any confusion with the results.
Frequently Asked Questions About How Long Benadryl Lasts
If you’re wondering how long Benadryl lasts, there’s a good chance you have additional questions. Here you’ll find some frequently asked questions about Benadryl use and misuse.
Is It Possible To Overdose On Benadryl?
Yes, it is possible to overdose on Benadryl. In fact, anybody who takes enough Benadryl to get high is at a major risk for drug overdose symptoms.
Is There A Lethal Dose Of Benadryl?
The lethal dose of Benadryl is estimated at 20 to 40 milligrams per kilogram (mg/kg) for adults and 500 mg/kg for children. However, fatal diphenhydramine overdoses are uncommon.
Why Might A Person Get High With Benadryl?
A person might get high from Benadryl for several reasons. Some people may accidentally consume too much Benadryl, even when taking it for allergies or cold symptoms.
Others have consumed large amounts of Benadryl as part of social media “challenges.”
Still, others may take Benadryl if they have another drug addiction but cannot access the drug that they are craving.
Do Medications Other Than Benadryl Contain Diphenhydramine?
Yes, diphenhydramine is the active ingredient in several medications.
Other medications that contain diphenhydramine include some motion sickness pills, drugs that induce sleepiness, and some cold medications.
Who Should Not Take Benadryl?
People with certain conditions should seek medical advice from a doctor before taking Benadryl.
These include pregnant and breastfeeding people as well as individuals who have heart problems, high blood pressure, or glaucoma.
Find Addiction Treatment Options
People who abuse Benadryl often combine it with other dangerous substances like opioids, antidepressants, or benzodiazepines. All of these drugs slow down the central nervous system, and using them together increases the risk of a potentially fatal overdose that requires emergency medical attention.
If you or someone you care about is engaging in Benadryl abuse or is facing addiction to multiple substances, professional help is available. Contact an addiction treatment specialist today to learn about your treatment options and take the first steps toward safe, effective recovery.
Addiction Resource aims to provide only the most current, accurate information in regards to addiction and addiction treatment, which means we only reference the most credible sources available.
These include peer-reviewed journals, government entities and academic institutions, and leaders in addiction healthcare and advocacy. Learn more about how we safeguard our content by viewing our editorial policy.
- Harvard Health Publishing
https://www.health.harvard.edu/blog/defusing-the-benadryl-challenge-discussing-danger-with-teens-2020110221286 - National Library Of Medicine
https://medlineplus.gov/druginfo/meds/a682539.html#side-effects - National Library Of Medicine
https://pubmed.ncbi.nlm.nih.gov/20838187/ - United States Food And Drug Administration (FDA)
https://www.fda.gov/safety/medical-product-safety-information/benadryl-diphenhydramine-drug-safety-communication-serious-problems-high-doses-allergy-medicine
