A single dose of the Diphenhydramine hydrochloride commonly referred to as Benadryl is very much active in the body/ system for between 4 and 6 hours on average. Usually, this drug is almost fully excreted from one’s body within 24 hours. A single dose of Benadryl is almost fully absorbed by your body, and it reaches the maximum activity within a period of one hour.

How Long does Benadryl Stay in your System

What is Benadryl?

Benadryl is the brand name for the diphenhydramine, which is an antihistamine. Doctors have recommended Benadryl as well as other diphenhydramine items to treat symptoms of allergy or even the hay fever such as a runny nose, itching in the nose or even throat, itchy eyes and sneezing. You can also be able to take Benadryl when you have symptoms as a result of the common cold.

Some people take Benadryl to be able to treat the motion sickness as well as a sleep aid. This OTC (Over the Counter) medication gets to block the action of the histamine, a substance that occurs naturally in the body which causes the allergy symptoms. Benadryl does come in the form of tablets, gel caps and liquid form. Also, there is some diphenhydramine which goes directly to the skin. Such creams usually ease the itching from bee stings, insect bites, sunburn, poison oak, poison ivy as well as other skin irritations.

Is it OK to take Benadryl as a sleep aid?

Many Doctors have always cautioned against the use of Benadryl as a sleeping aid. Drugs such as Benadryl have side effects such as an altered mental state, dry mouth, and urinary retention. While the side effects are mild and young patients with no medical problems can tolerate them, they do pose a great risk especially for the elderly. Use of antihistamines such as Benadryl can lead to parasomnias and also sleepwalking. The use of Benadryl for the long-term benefit has no long-term benefit and, most of the people develop a high tolerance very quickly.

How long does Benadryl stay in your system / Body?

Benadryl usually is cleared from the system for most people in a period of 24 – 48 hours. However, this can be extended in the elderly. While the Benadryl can be blamed for the side effects which it causes to people, there are other causes which need to be considered.

Side Effects

  • Benadryl has been prescribed to be able to treat the allergic reaction since it is capable of blocking the histamine that gets to be produced by the immune system. This particular antihistamine causes various side effects that range from the mild to the moderate and includes:

    Vertigo (dizziness)

  • Drug Interactions
  • A headache
  • You may experience paranoia and anxiety if you take Benadryl for a long time. It may happen with some users.
  • Dry oral and nasal cavities
  • Dysuria (difficulty urinating)
  • Drowsiness
  • Fatigue


Benadryl is not necessarily dangerous, but it is such a good idea to know exactly how long it is going to last in your system. This will be very important to help you ensure that you are not negatively impacted by medications side effects.

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