Can You Take Expired Benadryl?

Our pharmacist answers the latest question regarding whether or not it is okay to take expired Benadryl (diphenhydramine).


I have a bottle of Benadryl that I found but the expiration date is passed, it is about 3 years old. Will they still be effective for me to take?

Asked by Bing On Oct 22, 2017

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Oct 22, 2017
Benadryl Box With Text Overlay - Expired Benadryl


Generally speaking, it is not recommended to take expired drugs (past the manufacturer expiration date).

The main concern is that they may not have the same effectiveness or potency they had when they were in date.

You just don't know whether or not the medication is still good and there really isn't a perfect way to tell. Having effective medication is extremely important for certain situations that may be life-threatening.

If you needed Benadryl to stem an allergic reaction, it would prudent to always have a bottle that is in date so you know it will give you an effective dose.

Drug Expiration Dates

The official definition of the manufacturer's expiration date is as follows:

"The date beyond which ideally stored medications in the unopened manufacturer's storage container or in most circumstances, the opened and intact manufacturer's storage container, should not be used."

United States Pharmacopeia (USP)

The manufacturer's expiration date is usually expressed as the month and year, or as a day, month, and year. The manufacturer of the drug determines the day the drug will expire based on the clinical trials it does for that drug.

It almost never means that the drug goes "bad" after the date. The date on the bottle is the date up to which the manufacturer knows the drug still maintains its potency and safety as advertised. Simple as that!

In reality, a drug may be good for a long time after the listed expiration date, but there just haven't been any studies on it to know one way or the other.

Do Drugs Go Bad?

Most drugs don't actually go "bad" but they may have lost potency and thus will not have the desired effect as mentioned above.

Now, manufacturers typically use 2- to 3-year expiration dates because it is convenient. They don't need to perform longer stability tests...and the short dating assures the purchase of new drugs.[1]

They might not exactly know in 2-3 years the drug is longer good, but they will put that on the bottle so they do not have to perform stability tests for longer periods of time.

Harm from taking expired drugs is extremely rare has only been linked to degraded tetracycline. There are rare reports of kidney damage in patients who took outdated tetracycline in the 1960s.[2]

Also, some degraded drugs do have an altered taste or smell. For example, aspirin is left out too long, does degrade and has a foul odor associated with it when it is no longer good.[3]

Re-Packaged Drugs

In terms of drugs that have been repackaged (e.g. pharmacy dispensing into a prescription vial), a major regulatory body for pharmacy in the United States, known as USP, recommends no more than a one-year expiration date for drugs that are not in their original, unopened package.[4]

This is because re-packaged drugs (not in original bottle) don't have the light protection and the moisture absorbing qualities as pharmacy prescription vials do. All in all, your Benadryl (diphenhydramine) probably isn't bad or harmful, just not as effective.

Expired Benadryl

To sum everything up, Benadryl past its expiration date likely won't harm you (from the drug itself). There have been no reports of expired Benadryl causing harm and there is no indication that it breaks down into harmful components.

However, and this is an important point, it may not be as effective as it once was.

If you are relying on Benadryl to help reduce the symptoms of an allergic reaction, it would be prudent to have an 'in-date' product so you know it will have its stated potency and work as intended.


It is not recommended to take expired drugs (including Benadryl) because they may not be as potent as they once were. Taking expired Benadryl isn't known to cause harm, it just may not work as well, which is important when relying on the effects of the drug (e.g. to stem an allergic reaction).

  1. ^ Stability profiles of drug products extended beyond labeled expiration dates. PubMed
  2. ^ Tetracycline nephropathy. PubMed
  3. ^ Aspirin. PubChem
  4. ^ Expiration Dating of Unit-Dose Repackaged Solid Oral Dosage Form Drug Products. FDA

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Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Office: 716-389-3076

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