Can I Take Benadryl And Nyquil Together? | No, You Shouldn’t
Written By Kobi Nathan, Pharm.D., M.Ed., CDP, BCGP, AGSF
Sleep Disorders
May 5, 2023

Can Nyquil and Benadryl be taken together?

No! Taking both medications together can cause dangerous sedation, dry mouth, constipation, increased risk for falls and injuries, and worsen dementia.

Furthermore, Coupland and colleagues’ seminal work shows a clear association between chronic use of prescription and non-prescription anticholinergic drugs and the development of Dementia!

I cover these topics extensively in my other articles, linked below.

What are Benadryl and Nyquil?


Benadryl is an over-the-counter (OTC – non prescription)) antihistamine medication commonly used to treat allergy symptoms, such as sneezing, itching, and hives.

Some people take it as a sleep aid to manage their insomnia.


Vicks Nyquil is a popular OTC cold and flu medicine that helps to alleviate symptoms like coughing, sore throat, fever, and nasal congestion.

As all of us know, having the cold or the flu can make us feel miserable, affecting our ability to fall asleep (and stay asleep!).

The makers of Nyquil have included doxylamine, with its sedating properties, to help manage insomnia that can result from our bouts with these respiratory illnesses.

Managing insomnia, especially in older adults, is not easy.

Multiple issues could be contributing to the reason why you may be having trouble sleeping.

Many medications can interfere with the stages of sleep.

The biological changes that occur in all of us as we age can also cause sleep problems.

Medical problems that affect the central nervous system can also interfere with restful sleep.

I cover these topics extensively in my article on Insomnia in older adults here.

The Active Ingredients in Benadryl and Nyquil

Benadryl’s Active Ingredient: Diphenhydramine

Diphenhydramine is the active ingredient in Benadryl that acts as an antihistamine, reducing allergy symptoms by blocking the effects of histamine, a substance released by the body during an allergic reaction.

Nyquil’s Active Ingredients: Acetaminophen, Dextromethorphan, and Doxylamine Succinate

Nyquil contains three active ingredients that work together to provide relief from cold and flu symptoms:

  1. Acetaminophen: A pain reliever and fever reducer.
  2. Dextromethorphan: A cough suppressant that helps to control coughing.
  3. Doxylamine Succinate: An antihistamine that can help with sleep and reduce allergy symptoms.

To better understand the differences between these two medications, read my detailed article, Nyquil vs. Zzzquil.

The Dangers of Mixing Benadryl and Nyquil

Increased Side Effects

When taken together, Benadryl and Nyquil can (make that “will”) increase the risk of anticholinergic drug effects, as both medications contain first-generation antihistamines.

These side effects include:

  • Drowsiness.
  • Dizziness.
  • Dry mouth.
  • Blurred vision.
  • Difficulty urinating (in men).
  • Constipation.
  • Worsening of underlying cognitive impairment.

In medical speak, these are called anticholinergic effects.

These negative drug effects are a common thread in MANY preventable medical problems in older adults that lead to hospitalization and premature death.

Those of us who specialize in Geriatrics know this problem well and are constantly looking for medications contributing to an older adult’s anticholinergic burden.

Read my detailed articles below to get a good handle on these very important topics.

If you are an older adult or have older adult loved ones in your life, I highly recommend you read these posts:

Watch my video below to see how polypharmacy and anticholinergic burden can be safely eliminated with the help of a doctor or pharmacist:


The video below describes modifiable and non-modifiable risks of dementia:



Older adults are at increased risk for struggling with the Geriatric Syndromes, a constellation of health-related problems that are some of the most common causes of hospital admission and premature death.

I cover this topic in detail here.

OK, back to Nyquil and Benadryl…

Potential Drug Interactions

Besides the negative effects of combining Benadryl and Nyquil that I mentioned above, combining acetaminophen (found in Nyquil) with other medications containing the same ingredient can increase the risk of liver damage.

It’s important always to read the labels of medications to avoid potential drug interactions – I can’t stress this enough!

This article has an affiliate link. I may earn a small commission at no additional cost. Thank you for supporting my website!

Alternatives to Mixing Benadryl and Nyquil

Exploring alternative options is essential if you’re considering taking both Benadryl and Nyquil to alleviate your symptoms.

For instance, if you need an antihistamine for allergy relief and a cold or flu medication, consider choosing a cold and flu product that doesn’t contain an antihistamine, such as Dayquil.

This way, you can safely take Benadryl for allergies and Dayquil for cold and flu symptoms without increasing the risk of side effects or drug interactions.

There really is no valid reason for taking both Benadryl and Nyquil – if you must (and I highly recommend you don’t), just choose one or the other and stick with it.

If you want to try a sleep aid that does not contain anticholinergic drugs, I recommend Natrol melatonin products.

This is the brand my own sleep medicine doctor recommends to his patients, and it is the one I use myself.

You can check them out here.

Additionally, Magnesium is incredibly important for promoting GABA.

PerformanceLab, a company I trust, has a great sleep aid that contains three forms of Magnesium:

  1. Magnesium Bisglycinate – a chelated mineral form bound with glycine that enables greater intestinal absorption.
  2. Magnesium Taurate is magnesium bound to taurine, an amino acid promoting GABA for additional sleep onset support.
  3. NutriGenesis® Magnesium – a clean, probiotic-cultured magnesium complexed with absorption-boosting cofactors.

You can learn more about the product here.

Consult a Healthcare Professional

Before combining any medications, consulting with a healthcare professional, such as a pharmacist or doctor, is crucial.

They can provide guidance on the safe use of these medications and recommend alternative options if necessary.

Additionally, they can help you understand any potential risks and monitor for adverse effects or interactions.


While Benadryl and Nyquil are effective medications for their respective purposes, mixing them can lead to increased side effects and potential drug interactions.

Exploring alternatives and consulting with a healthcare professional before combining these medications is important.

Always read the labels and use medications as directed to ensure your symptoms’ safe and effective management.

Frequently Asked Questions (FAQs)

1. Can I take Benadryl and Nyquil at the same time?

It’s not recommended to take Benadryl and Nyquil together, as both medications contain antihistamines, which can increase the risk of side effects and potential drug interactions.

2. What can I take instead of combining Benadryl and Nyquil?

Consider taking a cold and flu medication that doesn’t contain an antihistamine, such as Dayquil.

This way, you can safely take Benadryl for allergies and Dayquil for cold and flu symptoms without increasing the risk of side effects or drug interactions.

You can also try melatonin products.

3. Can mixing Benadryl and Nyquil cause liver damage?

Mixing Benadryl and Nyquil may not directly cause liver damage; however, Nyquil contains acetaminophen, which can be harmful to the liver in high doses or when combined with other medications containing acetaminophen.

Always read medication labels and consult a healthcare professional to avoid potential risks.

4. Is it safe to take Benadryl and Nyquil together if I space them out?

While spacing out the medications might reduce the risk of side effects, it does not make sense to do so.

It’s still crucial to consult with a healthcare professional before combining these medications, as there may be a better alternative for managing your symptoms.

5. Can combining Benadryl and Nyquil cause drowsiness?

Combining Benadryl and Nyquil can cause increased drowsiness, as both medications contain antihistamines known to cause sedation. It’s essential to avoid driving or operating machinery when experiencing drowsiness due to medication use.

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