How Long Does Benadryl Stay In Your System [LAST STUDY]2 min read

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, the drug can have some severe side effects.

Before consuming Benadryl, it is good to take the time to evaluate the risks and effects of the medication.

Within this guide, you will learn exactly how long Benadryl last and how long it’ll remain in your system.

What Is Benadryl?

First and foremost, it is a good idea to learn the basics of this medication. Although it is more frequently referred to as Benadryl, the medical name is 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?

To understand exactly how long this medication will remain in your system, it is essential to learn about its half-life. 

This medication’s exact half-life can vary depending on several 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 multiply these figures by two 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 can block 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
  • The sensation of needing to urinate frequently
  • Drowsiness
  • Fatigue
  • Dysuria (difficulty urinating)
  • Some users may experience paranoia and anxiety when taking Benadryl over long periods.
  • Drug Interactions

It is crucial never to 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.


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 the medication’s side effects don’t negatively impact you.

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.

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