New Study – How Long Does Benadryl Stay In Your System

New Study – How Long Does Benadryl Stay In Your System

Almost everyone all around the world has used Benadryl at some point or another. This medication is commonly used for allergy purposes and it is typically very safe. However, it is possible for the drug to have some very serious side effects. Before consuming Benadryl, it is a good to take the time to evaluate the risks and effects of the medication. Within this guide, you will learn exactly how long does Benadryl last and how long it’ll remain in your system.

What Is Benadryl?
First and foremost, it is a good idea to learn about the basics of this medication. Although it is more frequently referred to as Benadryl, the medical name is actually diphenhydramine. It is an antihistamine and is commonly used for the alleviation of the symptoms of allergic reactions, as well as motion sickness. Although it is less common, Benadryl can also be used to help treat Parkinson’s disease.

How Long Does Benadryl Stay In Your System?

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In order to understand exactly how long this medication will remain in your system, it is essential to learn about the drug’s half-life. The exact half-life of this medication can vary depending on a number of different factors, including metabolism and age. Below, you will find the average high-life for each age group.

  • Children – 7 hours
  • Adults – 12 hours
  • Elderly – 17 hours

It should be known that the half-life helps to determine how long it’ll take for half of the drug to dissipate from your body. Therefore, you would need to multiple these figures by two, in order to get your answer. These answers will be provided below for your convenience.

  • Children – 14 hours
  • Adults – 24 hours
  • Elderly – 34 hours

On average, it’ll take a day for Benadryl to leave your system completely.

Side Effects

Benadryl is prescribed to treat an allergic reaction, since it is capable of blocking histamine, which is produced by the immune system. This antihistamine causes many different side effects, which range from mild to moderate and include the following:

  • Vertigo (dizziness)
  • Headache
  • Dry oral and nasal cavities
  • Sensation of needing to urinate frequently
  • Drowsiness
  • Fatigue
  • Dysuria (difficulty urinating)
  • Some users may experience paranoia and anxiety, when taking Benadryl over long periods of time.
  • Drug Interactions

It is crucial to never take Benadryl, when you are being prescribed a benzodiazepine (Xanax) and serotonin reuptake inhibitors (Prozac), because it can increase the side effects dramatically. This can also increase the risks of antihistamine overdose. Be sure to notify your physician, if you are currently taking a regimen of these drugs, before consuming Benadryl.


At the end of the day, Benadryl isn’t necessarily dangerous, but it is a good idea to know exactly how long it’ll last in your system. This will help to ensure that you aren’t negatively impacted, by the medications side effects. With this in mind, you should never consume this drug, before you head to work or when you’re going to drive a vehicle. Give yourself 24 hours, before partaking in any of these tasks.

David Warren
David Warren

Pharmaceutical specialist at
David Warren is a pharmaceutical specialist that dispenses prescription medication on a daily basis. He received a Bachelor of Science degree in pharmacy from the University of Tennessee in 1991. With over 50 publications on medication-related and pharmacy topics, David has been able to share his experiences and knowledge with others.

David with lots of experience and knowledge in medications that are utilized to treat a wide range of medical conditions. Before David dispenses a medication to a patient, he will go over the side effects, dosage recommendation and contraindications.
David Warren

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  1. Rae January 31, 03:58 Reply
    I don't think that's how half lives work...
  2. gamiebears April 27, 07:24 Reply
    I had an adverse reaction to iodine and I was given some benadryl. The hives went away, I got sleepy and confused. The one thing that is bothering me still and it has been over 24 hours, is that I have now having pvcs. I am 57 and confused. One doctor says don't worry about it. But I am still concerned. Has anyone else had pvcs after taking this drug
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