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Antihistamines and CBD Oil Interaction: Side Effects and More

Animals. Pollen. Dust. No matter what stokes your sneezes, having an allergic response to your environment can be much more life-altering than non-sufferers may realize.

If you’re reliant on a daily antihistamine to keep your symptoms at bay, you may be wondering whether you can safely add CBD oil to the equation.

Here you'll find a medically reviewed explanation of how CBD oil may potentially interact with some of the most commonly used antihistamine medications. This information will help you make an informed decision as to whether or not CBD oil is right for you.

The information contained in this page is meant to serve as an educational tool and should not be substituted for medical advice.

How CBD Oil Reacts to Antihistamines

While the majority of research indicates that CBD oil is safe for use and has little to no side effects, it can pose risks if you are taking certain medications, specifically those that act on the cytochrome P-450 enzyme system.

The P-450 system is responsible both for the detoxification of foreign chemicals as well as the metabolism of many common medications. CBD oil, along with grapefruit and certain other natural compounds, like St. John’s Wort, have been shown to inhibit the P-450 system. When the P-450 system is inhibited, medications take longer to be metabolized and so levels of drug substrates can accumulate in your blood.

Because antihistamines use the P-450 system, using them with CBD oil can slow down your body’s ability to break them down. This causes more antihistamine to be present in your system at any given time, which increases the chances you’ll experience side effects.

So, if you’re a daily antihistamine user, you should use caution and speak with your doctor before adding CBD oil to your regimen. The benefits of cannabidiol (CBD) may not outweigh the side effects of combining it with your antihistamine medication.

Side Effects Of CBD Oil And Antihistamine Interaction

The most widely used antihistamines contain one of the following key ingredients: loratadine, cetirizine, fexofenadine or diphenhydramine. Each works differently in the body to produce a similar outcome, and each comes with a range of potential side effects. Your chances of experiencing these side effects may be increased when combining your medication with CBD oil.

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This table breaks down common antihistamines and their side effects, and how CBD oil could influence the likelihood of experiencing them.

Generic Antihistamine Name Common Brands Possible Side Effects Possible Side Effects When Used With CBD Oil
Loratadine Claritin; Allerclear Headache; stomach pain; insomnia; dry mouth; nervousness CBD oil increases the risk and/or severity of side effects
Cetirizine Zyrtec; Alleroff Drowsiness; stomach pain; vomiting; diarrhoea CBD oil increases the risk and/or severity of side effects
Fexofenadine Allegra Headache; vomiting; body pain; dry mouth CBD oil increases the risk and/or severity of side effects
Diphenhydramine Benadryl; Sominex Drowsiness; vomiting; loss of appetite; constipation CBD oil increases the risk and/or severity of side effects

Before taking CBD oil products with any antihistamine medications, it is important to consider the potential side effects. If drowsiness is a potential side effect that could be exacerbated when CBD oil is added to the mix, it would be a good idea to avoid driving, operating heavy machinery, or undertaking any task that requires alertness or concentration while taking both the antihistamine and CBD oil. Consider the side effects and plan accordingly.

Elderly users or individuals taking multiple medications such as antihistamines that have central nervous system or respiratory-depressant effects should be monitored closely as these effects can be amplified when CBD oil is added to the equation. This also applies if you’re taking medication for high blood pressure, since cannabidiol is also known to counteract hypertension.

If you’ve experienced side effects when taking antihistamines in the past, avoiding CBD oil while on them is probably a smart idea.

It is entirely possible that you will not be impacted negatively but until you know for sure, use CBD oil with caution if you’re taking antihistamines.

Effectiveness of Using CBD Oil with Antihistamines

There is a wide range of potential health benefits of CBD oil, some of which are particularly promising for allergy sufferers.

For starters, CBD oil may reduce seasonal allergies. Cannabidiol helps regulate the function and production of white blood cells, which play a key role in the inflammatory response to potential allergens. CBD oil is anti-inflammatory and antimicrobial, making it ideal for irritated sinuses and airways. In fact, CBD has been studied for its potential to reduce allergy-induced inflammation in asthma sufferers.

Keep in mind that there are moderate risks associated with using CBD oil with antihistamines and you will need to decide if the potential benefits outweigh these potential risks.

If you’d like to explore the option further, first speak to your doctor about combining the two. You can also talk to a naturopathic doctor who specializes in using cannabidiol for medical treatments.

Best CBD Oils for Allergy Sufferers

If your physician confirms it’s okay to take CBD oil with your allergy medication, you’ll want to find the best-quality CBD oil out there.

Start by finding a brand that produces organically grown products so you know your CBD oil will be free of pesticides. You’ll also want to look for CBD companies that use third-party laboratory testing to verify the potency and purity of their products. The third-party lab reports are known as Certificates of Analysis and provide a nice breakdown of all the compounds—good and bad—found in each batch of a company’s CBD product. If you come across a CBD brand that does not provide Certificates of Analysis, it’s time to shop elsewhere.

Once you have a CBD company picked out, you’ll need to decide how you’d like to take your cannabidiol.

CBD oil capsules and edibles make for an easy way to include CBD oil as part of your daily routine, perhaps pairing them with your morning coffee. The only downside to taking CBD in an edible form is you’ll have to wait longer to feel the benefits, as the CBD needs to pass through your digestive system. The effects of a CBD capsule or edible will typically last for 4-6 hours, making this an ideal delivery method if you suffer from chronic allergies.

A CBD vape pen is a great option for taking CBD oil if you need it throughout the day as it’s the fastest-acting delivery format. CBD oil drops and tinctures will not set in as quickly as a vape pen, but you’ll feel the benefits for a relatively longer period of time.

If you typically have suddenly occurring allergy symptoms, a CBD vape or oil may be your best option. In both these instances, the CBD does not have to pass through your digestive system before being absorbed into the bloodstream, so the onset of action is very swift. 

Finally, if you get itchy allergic rashes or hives, it might be worth investing in a CBD oil topical cream. This cream can work directly on the affected area, providing targeted relief over the course of a whole day.

CBD Oil Dosage

In terms of dosage, follow the recommendation provided on your CBD product’s information leaflet. While the ideal dose of CBD oil will depend on a range of individual factors such as your weight and metabolism, at CBD Oil Review we have analyzed hundreds of products and come up with a standard serving suggestion:

The CBD Oil Review Serving Standard is 25mg of CBD, taken twice daily.

If you are not getting results from this amount, we recommend increasing the serving size by 25mg every 3-4 weeks until you find relief.

If in doubt, always speak to a medical professional before combining treatment options. If you’d like more information on dosages and some useful tips for getting it right, check out our dosage guide here.

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+ 1 sources


  1. Francieli Vuolo et al. (2015) Evaluation of Serum Cytokines Levels and the Role of Cannabidiol Treatment in Animal Model of Asthma - National Library of Medicine https://pubmed.ncbi.nlm.nih.gov/26101464/

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