How Long Does Diphenhydramine (Benadryl) Stay in Your System?

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Updated October 28, 2024

Authored By:

Joe Gilmore

Edited By

Amy Leifeste

Medically Reviewed By

Javier Rodriguez-Winter

Authored By:

Joe Gilmore

Edited By

Amy Leifeste

Medically Reviewed By

Javier Rodriguez-Winter

woman thinking representing can you overdose on birth

Benadryl, also known as diphenhydramine, is a medication that helps with allergies. You can buy it at grocery stores, drug stores, and pharmacies without a prescription. While it’s good for treating allergies, some people use it to feel high, which can lead to dependence.

Diphenhydramine’s half-life tells us how long Benadryl lasts, and how long it stays in your body. This can change based on your weight, age, and how much you take. Read on and find out:

  • How long does Benadryl stay in your system?
  • How long does it take for Benadryl to wear off?
  • And how to get compassionate and effective addiction treatment if you’re struggling with substance abuse

 

What Is Benadryl?

Benadryl is a medication used to help with allergies and colds. It comes in different forms like pills and creams. Benadryl is a type of drug called an antihistamine.

The FDA (U.S. Food and Drug Administration) approves Benadryl for use by adults and some kids to help with:

  • Allergies
  • Seasonal allergies like hay fever
  • Itchy skin
  • Common cold

 

Diphenhydramine

Diphenhydramine is the generic name for Benadryl. It works the same way as Benadryl to help with allergies and colds. You can find diphenhydramine in many stores, just like Benadryl.

 

When To Take Benadryl

Benadryl is a helpful medication when used correctly. It is used to treat various conditions.

 

Allergies

If you have allergies, Benadryl can help. This includes allergies to pollen, pet dander, dust, or certain foods. Benadryl helps reduce symptoms like sneezing, runny nose, and itchy eyes.

 

Hay fever

Hay fever, also known as seasonal allergies, happens at certain times of the year. If you feel sneezy and have a runny nose when plants are blooming, Benadryl can help you feel better.

 

Common cold

Benadryl can also be used for the common cold. It helps with symptoms like a runny nose and sneezing. However, it won’t cure the cold – it just makes you feel more comfortable.

 

Itchy skin

If you have itchy skin from bug bites, hives, or rashes, Benadryl can help stop the itching. It can also help with itching caused by other skin conditions.

 

Motion sickness

Some people use Benadryl to help with motion sickness. If you feel sick when traveling by car, plane, or boat, Benadryl can help you feel better.

 

Insomnia

Sometimes, people use Benadryl to help them sleep. It can make you feel drowsy, so it might help if you have trouble falling asleep. But it’s not a long-term solution for sleep problems.

 

Always follow the instructions on the package or those given by your doctor. Here are some general tips:

  • Take the right dose. Do not take more than recommended.
  • If you’re using the liquid form, use the measuring cup that comes with it.
  • If you’re giving Benadryl to a child, make sure it’s safe for their age and give the correct dose.

 

Side Effects of Benadryl

While Benadryl can help with many symptoms, it can also cause side effects. Here are some common and some serious side effects:

  • Drowsiness: One of the most common side effects is feeling very sleepy. This can make it hard to stay awake and alert.
  • Dizziness: You might feel dizzy or lightheaded after taking Benadryl.
  • Dry mouth: Your mouth might feel dry, and you may need to drink more water.
  • Blurred vision: Benadryl can make it hard to see clearly. Your vision might become blurry.
  • Constipation: You might have trouble going to the bathroom. Drinking water and eating fiber can help.
  • Trouble peeing: Some people find it hard to pee after taking Benadryl.

 

In rare cases, Benadryl can cause serious side effects. Here are some to watch out for:

  • Severe allergic reaction: Though it treats allergies, some people might be allergic to Benadryl itself. Symptoms include rash, itching, swelling, severe dizziness, and trouble breathing. Get medical help right away if this happens.
  • Confusion: Especially in older adults, Benadryl can cause confusion and trouble thinking clearly.
  • Fast heartbeat: Your heart might start to beat very fast or in an uneven way. This can be scary and needs medical attention.
  • Seizures: In very rare cases, Benadryl can cause seizures. This is a medical emergency.

 

To help avoid side effects, follow these tips:

  • Take Benadryl only when needed and as directed.
  • Avoid alcohol while taking Benadryl, as it can increase drowsiness.
  • Do not mix Benadryl with other medications without asking a doctor.
  • Drink plenty of water to help with dry mouth and constipation.
  • Be careful when driving or operating machinery, as Benadryl can make you sleepy.

 

How Long Does Diphenhydramine Last?

The time Benadryl stays in your body depends on its half-life, which varies from person to person. On average, Benadryl can stay in your system for about 2.4 to 9.4 hours. This means it takes this long for your body to get rid of half of the drug.

It might take about 13.2 to 49 hours to completely remove Benadryl from your body. It can show up in drug tests up to 2 days after you take it.

The highest amount of Benadryl is in your body 2 to 4 hours after taking it. This is when you might feel the side effects the most, but how bad they are can be different for everyone.

 

How to Make Benadryl Wear Off Faster

If you want Benadryl to wear off faster, here are some tips:

  • Drink lots of water to help flush it out of your system.
  • Eat healthy foods to boost your metabolism.
  • Stay active with light exercise to speed up the process.
  • Always talk to a doctor before trying these tips to ensure they are safe.

 

5 Factors That Affect How Long Benadryl Lasts

Different things can change how long Benadryl stays in your body. Here are five important factors:

 

1) Age

Younger people often process drugs faster than older people. As you get older, your body might take longer to get rid of Benadryl.

 

2) Weight

Your weight can affect how long Benadryl stays in your system. If you weigh more, it might take a bit longer for the drug to leave your body.

 

3) Dosage

The amount of Benadryl you take matters. Higher doses can stay in your body longer than smaller doses.

 

4) Metabolism

Metabolism is how your body changes food and medicine into energy. If you have a fast metabolism, you might get rid of Benadryl quicker. If your metabolism is slow, the drug might stay longer in your system.

 

5) Health

Your overall health can impact how long Benadryl lasts. If you have liver or kidney problems, it might take longer for your body to process and eliminate the drug. Staying healthy can help your body work better.

Knowing these factors can help you understand why Benadryl might last longer in some people than in others. Always talk to your doctor if you have questions about how long Benadryl will affect you.

How long does diphenhydramine last Benadryl half life

Dangers of Benadryl Misuse

Using Benadryl in the wrong way can be very dangerous. Here are some risks if you misuse Benadryl:

 

Dependence

Some people use Benadryl to feel a high. Doing this too often can make your body depend on the drug, meaning you need to take it more and more to get the same effect.

 

Overdose

Taking too much Benadryl can lead to an overdose. Symptoms of an overdose include extreme drowsiness, confusion, dry mouth, larger pupils (black circles in your eyes), and even seizures.

 

Heart problems

Misusing Benadryl can cause heart problems. Your heart might start beating too fast or unevenly, which can be very serious.

 

Mental confusion

Taking too much Benadryl can make you feel very confused and disoriented. This can be dangerous, especially if you need to drive or operate machinery.

 

Severe drowsiness

Benadryl can make you very sleepy. If you take too much, you might find it hard to stay awake or pay attention. This can be risky, especially when you need to stay alert.

 

Accidents

Because Benadryl can make you drowsy and confused, it increases the chances of accidents. You could fall, hurt yourself, or get into a car crash if you drive while under the influence of Benadryl.

 

Mixing with other drugs

Mixing Benadryl with other drugs or alcohol is very dangerous. It can make the side effects much worse and can be life-threatening.

 

Overdose Symptoms of Benadryl

Taking too much Benadryl can be very dangerous. Here are some signs and symptoms of a Benadryl overdose:

  • Extreme drowsiness: You might feel sleepy and find it hard to stay awake.
  • Confusion: You may feel confused and not know where you are or what’s happening around you.
  • Dry mouth: Your mouth might feel very dry, and you might find it hard to swallow.
  • Larger pupils: The black circles in the middle of your eyes, called pupils, might get bigger than normal.
  • Blurred vision: You might have trouble seeing clearly and everything might look fuzzy.
  • Fast heartbeat: Your heart might start beating very quickly or in an uneven way, which can be very scary.
  • Seizures: In serious cases, an overdose can cause seizures. This means you might shake uncontrollably and lose control of your body.
  • Hallucinations: You might see or hear things that aren’t really there, which can be very frightening.
  • Trouble peeing: You might find it hard to pee or feel like you need to go but can’t.

 

If you think someone has taken too much Benadryl, it’s important to get help right away. Here’s what you should do:

  • Call 911 or go to the nearest emergency room.
  • Tell the doctors exactly what was taken and how much.

 

Knowing the signs of a Benadryl overdose can help you act quickly and get the help that’s needed. Always take medicines like Benadryl exactly as directed to avoid these dangerous situations.

 

Benadryl’s Interactions With Other Substances

When you drink alcohol or take other medications with Benadryl, it becomes harder for your body to remove the drug. Alcohol makes Benadryl stay in your body longer and makes its side effects worse. This is why mixing alcohol with Benadryl is very dangerous.

Alcohol affects the liver, which helps process Benadryl. When your liver is busy with alcohol, it can’t get rid of Benadryl properly. Both alcohol and Benadryl affect your brain and can make you feel confused and very sleepy.

Because both sedate your brain, you won’t be able to think or move properly. Avoid driving, as it will be hard to control your car safely.

Benadryl interacts with over 400 different drugs. Examples of severe interactions include:

  • Antihistamines like hydroxyzine and loratadine: You may feel sleepy and confused.
  • Anticholinergic drugs: You may have dry mouth, blurry vision, trouble remembering things, and even hallucinations.
  • Antipsychotic drugs: You could feel more confused, and agitated, and experience hallucinations.
  • Benzos like Xanax and Valium: You may feel dizzy and lightheaded, have slurred speech, and slow reactions.
  • Opioids: You might have constipation, feel very happy or euphoric, feel nauseous, and have slower breathing.

 

Always talk to a doctor before mixing Benadryl with other medications or alcohol.

 

How Long Does Benadryl Stay In Your System? | FAQs

 

How Long Do Antihistamines Stay in Your System?

Antihistamines like Benadryl can stay in your system for a while, depending on the type and your body. Generally, they can last from a few hours to a day or more. The time it takes to clear out can be different for each person based on factors like age, weight, and health.

 

How Long Does It Take for Benadryl to Wear Off?

Benadryl usually starts to wear off after 4 to 6 hours. However, you might still feel some effects for up to 8 hours. This can vary depending on how your body processes the drug.

 

How Long Does It Take for 25mg of Benadryl to Wear Off?

A dose of 25mg of Benadryl generally starts to wear off after 4 to 6 hours. You might still feel some drowsiness or other effects for a bit longer, depending on your body’s reaction.

 

What Is Benadryl Half-Life?

Benadryl’s half-life is the time it takes for half of the drug to leave your system. On average, the half-life of Benadryl is between 2.4 and 9.4 hours. This means your body takes this time to get rid of half of the dose you took.

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Get Treatment for Drug & Alcohol Addiction at Gratitude Lodge

If you have been abusing any addictive substance, we can help you get back on track with immersive inpatient treatment at Gratitude Lodge in Southern California. We have luxury rehabs in Newport Beach and Long Beach, California.

During medical detox at Gratitude Lodge, medications and 24/7 care make the withdrawal process safer and easier. You can then move into an ongoing inpatient program at one of our rehabs by the beach.

All addictions present differently, so all our programs offer personalized therapies, such as:

  • MAT (medication-assisted treatment)
  • Counseling
  • Talk therapy
  • Family therapy
  • Group therapy
  • Holistic therapy
  • Aftercare

 

Call our recovery experts today at 844-576-0144.

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Jenni Bussi

Jenni Busse MS, LPCC

Jenni Busse MS, LPSS is the Clinical Director at Gratitude Lodge. Jenni oversees the clinical program and the clinical team at Gratitude Lodge as a whole. Jenni has worked in treatment for almost 14 years. Her background as a licensed therapist and her passion for helping others intersected with addiction recovery when she started working primarily in detox residential treatment.
Joe Gilmore

Joseph Gilmore

Joseph Gilmore has been working in the addiction industry for half a decade and has been writing about addiction and substance abuse treatment during that time. He has experience working for facilities all across the country. Connect with Joe on LinkedIn.

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