How Long Does Diphenhydramine Stay in Your System?

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Last Updated on: 27th February 2024, 07:45 pm

It’s not uncommon for those of us on the path to recovery or even just in everyday life to have questions about over-the-counter (OTC) medications like diphenhydramine. Whether you’ve taken it to alleviate allergy symptoms or as a sleep aid, you may be curious about its effects and how long it stays in your system. Today, we’re diving into the nitty-gritty of diphenhydramine and its presence in your body.

What is Diphenhydramine?

Diphenhydramine is an antihistamine commonly used to treat allergy symptoms. Many people recognize it as the active ingredient in OTC drugs like Benadryl. Apart from allergies, it’s often used as a sleep aid, given its sedative properties.

How Long Does Diphenhydramine Stay in Your System?

A drug’s half-life is when it takes half of the drug to be eliminated from your system. Diphenhydramine has an average half-life of about 2 to 8 hours. This means that for most people:

  • After 2 to 8 hours: 50% of the drug is eliminated.
  • After 4 to 16 hours: 75% is gone.
  • After 6 to 24 hours: 87.5% is cleared.

And so on…

For most individuals, diphenhydramine will be almost completely eliminated from the body within 1-2 days. However, various factors can influence how quickly the drug is metabolized, such as age, liver function, dosage, and more.

Detection in Drug Tests

Although diphenhydramine is legal and available OTC, it might be relevant for some to know if it shows up on drug tests. In general, standard drug tests do not specifically look for diphenhydramine. However, it’s worth noting that in rare cases, diphenhydramine can lead to false positives for benzodiazepines or PCP on certain tests. If you’re scheduled for a drug test, it’s always a good idea to provide a list of all medications you’re taking, including OTC ones.

The Importance of Knowing

Knowledge is power, especially when it comes to what we put in our bodies. Being informed helps ensure safety, especially for those in recovery or undergoing drug treatments. It’s essential to avoid potential drug interactions or side effects.

Seek out a Medical Professional

Diphenhydramine, like all drugs, needs to be taken responsibly. While it exits the system relatively quickly, knowing how it affects you and interacts with other substances is crucial. Always consult with a medical professional about any medications, even if they’re over-the-counter.

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Do you or a loved one have questions or need support related to substance use, dual diagnosis, or recovery? At OC Revive, we’re here to help. Reach out to us at 844-954-3890. Your path to healing and understanding starts with a single call.


Diphenhydramine is an antihistamine most often used to treat allergy symptoms such as sneezing, runny nose, itching, and watery eyes. It is also widely used as an over-the-counter sleep aid due to its sedative properties.

Yes, some common side effects of diphenhydramine include drowsiness, dizziness, constipation, stomach upset, blurred vision, and dry mouth/nose/throat. If any of these symptoms persist or worsen, it’s essential to consult with a healthcare professional.

It’s crucial to consult with a healthcare provider or pharmacist before combining diphenhydramine with other medications. Diphenhydramine can interact with several other drugs, especially alcohol, other antihistamines, and certain antidepressants.

While occasional use of diphenhydramine for allergies or sleeplessness is generally considered safe for most people, chronic daily use is not recommended without a doctor’s supervision. Prolonged use can lead to tolerance, meaning increased dosages are required for the same effect and potential dependency.

While diphenhydramine isn’t typically screened for in standard drug tests, it can, in rare cases, lead to false positives for benzodiazepines or PCP. If you’re taking diphenhydramine and are scheduled for a drug test, it’s advisable to inform the testing entity about all the medications and supplements you’re currently taking.

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