Is it Safe to Take Both Benadryl and Weed?

weed and benadryl
By Nick Congleton Updated March 8th

Medically reviewed by Dr. Brian Kessler, MD

Fact-checked by Alexandra Arnett, MS

Antihistamines, like Benadryl, are popular solutions for battling common seasonal allergy symptoms and colds. They can even relieve insomnia that may come with nasal congestion, headaches, and the other hassles associated with colds and allergies. 

Because so many people rely on antihistamines to help with cold and allergy symptoms, many cannabis consumers are left wondering: Is it safe to use Benadryl and cannabis at the same time?

There isn’t much scientific research that directly addresses the question. Still, by looking into how cannabis and Benadryl interact with the body, it’s possible to draw conclusions about the possible risks and benefits of using both simultaneously. 

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What is Benadryl?

Antihistamines are a class of drugs commonly used to treat allergy symptoms. They work by blocking histamine, a chemical the immune system naturally produces. Too much histamine causes the body to overreact to common allergens, like pollen, causing allergy symptoms. 

Benadryl is a brand name associated with diphenhydramine, a prevalent form of antihistamine that’s behind several other big brand names, like Allergia-C, Nytol, and Unisom. Diphenhydramine is the active ingredient in Benadryl, making it the substance that could potentially interact with cannabis.

Like other antihistamines, diphenhydramine is typically taken to treat cold and allergy symptoms. Because drowsiness is a common side effect of diphenhydramine, it is sometimes also used as a sleep aid to treat insomnia. Many “nighttime” or “PM” versions of over-the-counter medications include diphenhydramine for this reason.

Symptoms commonly treated with diphenhydramine include:

  • Red, irritated, or itchy eyes
  • Watery eyes
  • Runny nose
  • Sneezing
  • Sinus congestion
  • Minor throat irritation
  • Motion sickness
  • Insomnia

Diphenhydramine is generally considered to be very safe and is sold over the counter. However, there are some common side effects associated with the drug. Those include:

  • Dryness in the mouth, nose, and throat
  • Drowsiness
  • Dizziness
  • Nausea
  • Vomiting
  • Constipation
  • Loss of Appetite
  • Headaches
  • Increased chest congestion
  • Muscle weakness
  • Nervousness
  • Excitement (This is more common in children.)

Diphenhydramine has also been associated with a few severe side effects, including:

  • Difficulty or pain when urinating 
  • Vision problems

Benadryl and Weed Interaction

Despite how familiar both cannabis and Benadryl are, there isn’t much research into their interactions, leading experts to focus on their potential to produce more pronounced effects. In essence, since cannabis and Benadryl can cause some of the same side effects, it’s possible they can amplify one another, making those same effects more severe.

Benadryl can cause drowsiness, dizziness, lightheadedness, and even confusion. Cannabis is known to cause similar symptoms, especially when consuming high doses of THC or CBD. In theory, even if Benadryl and cannabis don’t directly interact with one another, the combination could result in stronger side effects. It would stand to reason, for example, that combining Benadryl with a cultivar high in terpenes like myrcene or linalool (known for causing sleepiness) could create more substantial sedative effects.

Is There a Benefit to Taking Benadryl with Weed?

Benadryl and Weed

Because Benadryl and cannabis can produce some of the same side effects, many medical practitioners urge caution, noting that combining the two products could produce more pronounced effects. 

But could some of those enhanced effects be beneficial? Or are there other ways cannabis may help supplement Benadryl for some allergy sufferers?

While cannabis isn’t known to relieve allergy symptoms directly, it has shown promise in helping alleviate some symptoms, like inflammation, headaches, and difficulty sleeping. 

Inflammation is one of the driving forces behind many allergy symptoms, like puffiness around the eyes, sinus congestion, and headaches. Some studies show that cannabinoids, like CBD and CBG, have anti-inflammatory properties on their own.1 Others suggest that THC can also help fight inflammation and that the entourage effect works on inflammation as well, amplifying the inflammation-fighting potential of cannabis.2

The potential for cannabis to reduce inflammation may also make it useful in alleviating pain, like soreness and headaches, that may result from severe allergies. So, while cannabis doesn’t fight allergy symptoms the same way as Benadryl, it may help tackle the same problems indirectly. 

While stronger effects seem like a welcome result for some consumers, and there is some potential that cannabis and Benadryl could work together in the right circumstances, the risks shouldn’t be underestimated. Consumers who are having trouble achieving their desired results from Benadryl should speak with their doctor before adding cannabis to their treatment regimen.

What are the Risks of Using Benadryl and Marijuana?

weed and Benadryl

Most of the concern about combining Benadryl and weed comes down to their shared effects. While “stronger allergy relief” may sound like a positive, the combination could also result in stronger side effects. And when those side effects include drowsiness and confusion, the result can be dangerous for consumers.

Benadryl is often used to fight mild insomnia. It’s so well known for its ability to cause drowsiness that it’s often used in the “PM” versions of many over-the-counter medications. It’s even used independently as a sleep aid in products like Unisom.

Cannabis has also earned a reputation for making people sleepy. Experts warn that using both together can increase the drowsiness effects in often unpredictable ways. While it might be possible to anticipate the sleepiness caused by either cannabis or Benadryl independently, it’s extraordinarily difficult to predict how intense the effects will be – or how quickly they will affect users – when the two are combined. As a result, the potential for severe adverse effects due to sleepiness increases dramatically. 

Another concern is that it’s possible (though uncommon) to be allergic to cannabis. As with other plants, cannabis can trigger allergies that can range from mild, like typical seasonal allergies, to more severe. Using Benadryl with cannabis might help alleviate some of the allergic symptoms, but it could also mask others, resulting in consumers continuing to consume cannabis despite being allergic. While a cannabis allergy is considered to be rare, it remains a potential risk. 

If you are struggling with allergies and considering the use of cannabis and Benadryl, contact your doctor.

What About CBD and Benadryl?

CBD is extremely popular. It's federally legal and, therefore, more accessible. It also has demonstrated the potential to bestow many of the benefits of high-THC cannabis without the intoxicating effects, making it more applicable during the day or while traveling.

Some reported benefits of CBD, like fighting inflammation and insomnia, also overlap with the effects of Benadryl. For this reason, many of the same risks and potential benefits that come with combining high-THC weed and Benadryl still apply when using pure CBD products.

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Safety Tips When Using Benadryl and THC

There isn’t enough data to say whether or not using cannabis and Benadryl together is safe. While both substances are generally considered safe on their own, the two could interact in the body to amplify certain effects, like drowsiness and confusion. 

If you don’t have the option to use only one of these medications at a time, or if you are actively trying to increase the strength of Benadryl’s allergy-fighting effects, it is important to consult with your doctor to receive the best possible medical care and guidance.


1. Henshaw FR, Dewsbury LS, Lim CK, Steiner GZ. The Effects of Cannabinoids on Pro- and Anti-Inflammatory Cytokines: A Systematic Review of In Vivo Studies. Cannabis and Cannabinoid Research. 2021;6(3):177-195. doi:

2. Anil SM, Peeri H, Koltai H. Medical Cannabis Activity Against Inflammation: Active Compounds and Modes of Action. Frontiers in Pharmacology. 2022;13. doi:

The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.

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