CBD and Antihistamines (e.g. Claritin, Lorano, Zyrtec, Cetirizine)
David ReichUpdated:Key points at a glance:
CBD is sometimes used alongside antihistamines. The likelihood of drowsiness depends on the specific active ingredient. Loratadine and cetirizine are generally considered more cautious options, while diphenhydramine is strongly associated with increased sedation. Fexofenadine is typically regarded as a low‑sedation option. CBD may interact with enzymes such as CYP3A4 and CYP2C19, as well as with certain transport proteins. It is advisable to start with a low dose and try combinations in the evening. Avoid driving or operating machinery until you know how you are affected. Alcohol may intensify drowsiness. Taking products at different times does not reliably prevent possible enzyme‑related interactions. Speak to a doctor or pharmacist for individual advice.
CBD and antihistamines such as Claritin, Lorano, Zyrtec and cetirizine can often be taken together, but the risk of tiredness and potential CBD drug interactions depend strongly on the specific antihistamine and on your individual sensitivity. CBD can influence liver enzymes (especially CYP3A4 and CYP2C19) that are involved in drug metabolism, which may theoretically affect how some antihistamines are processed in the body. Because of this, medical guidance and cautious self‑monitoring are important when combining CBD with prescription medicines or over‑the‑counter allergy tablets.
CBD and antihistamines can sometimes be used together, but the risk of drowsiness and interactions differs between active substances. Loratadine or cetirizine are generally viewed as more cautious options; with 1st generation antihistamines such as diphenhydramine the risk of sedation is high. Start with a low CBD dose, first try the combination in the evening, and discuss it with your doctor or pharmacist.
How CBD and antihistamines work in the body
CBD (cannabidiol) is a naturally occurring compound from the cannabis plant. It interacts with the endocannabinoid system (ECS), which is involved in processes such as mood, pain perception, sleep and immune responses. CBD is available in products such as CBD oil as a food supplement or wellness product.
Antihistamines block histamine H1 receptors and in this way help to relieve typical allergy symptoms such as sneezing, itching, a runny nose and watery eyes. They are broadly divided into two generations:
- 1st generation (e.g. diphenhydramine, dimetindene – often strongly sedating and anticholinergic
- 2nd generation (e.g. loratadine, cetirizine, fexofenadine) – little to non‑sedating for most people
More on how CBD works and the ECS
Why is this relevant for CBD and antihistamine combinations? CBD can influence certain liver enzymes in the CYP450 system (including CYP3A4 and CYP2C19) as well as transporters such as P‑glycoprotein. As a result, blood levels of some medicines could theoretically increase, or their breakdown could be delayed. The potential for CBD metabolism interactions varies depending on the antihistamine: substances with strong CYP metabolism or pronounced sedative effects may be more sensitive.
In addition, there is a possibility of additive tiredness – even if there is no strong effect on liver enzymes. CBD itself can cause drowsiness in some people; combined with sedating antihistamines, this may reduce your ability to drive or operate machinery safely.
CBD can inhibit CYP450 liver enzymes such as CYP3A4 and affect transporters like P‑glycoprotein. Depending on the antihistamine, this may theoretically alter drug metabolism and increase side effects such as tiredness.
CBD and individual antihistamines: interaction overview
| Active substance (examples) | Sedation risk with CBD | Possible mechanism | Recommendation |
|---|---|---|---|
| Loratadine (e.g. Lorano/Claritin) | low–medium | CYP3A4 (metabolism) | Start low with CBD; titrate slowly and watch out for tiredness |
| Cetirizine/levocetirizine (e.g. Zyrtec/Xyzal) | medium (additive) | Low CYP metabolism, mainly additive sedation | First test the combination in the evening; avoid before driving |
| Fexofenadine (e.g. Telfast) | low | P‑glycoprotein/transporters | Be cautious with high CBD doses and if you take other interacting medicines |
| Diphenhydramine/dimetindene | high | Additive sedation + anticholinergic effects | Avoid the combination where possible; clarify with a doctor |
CBD and loratadine (e.g. Lorano, Claritin)
Loratadine is partly metabolised via CYP3A4. As CBD may inhibit this liver enzyme, there is a theoretical potential for increased loratadine plasma levels or prolonged effect. In everyday use, possible additional tiredness is usually the most relevant concern, although loratadine is generally considered non‑sedating.
If you combine CBD oil with loratadine:
- Start CBD with a low dose
- Increase gradually and according to your needs
- Watch out for drowsiness, especially at higher CBD doses
CBD and cetirizine/levocetirizine (e.g. Zyrtec, Xyzal)
Cetirizine and levocetirizine are largely excreted unchanged by the kidneys and are only minimally metabolised via CYP enzymes. The risk of a CBD liver enzyme interaction therefore appears lower.
However, additive sedation remains important: cetirizine can make some people feel sleepy, and CBD may intensify this. This is particularly relevant for activities requiring alertness (e.g. driving, operating machinery, exams).
When using CBD with cetirizine or levocetirizine:
- First test the combination in the evening
- Avoid taking it for the first time before important tasks or driving
- Monitor for increased tiredness or dizziness
CBD and fexofenadine (e.g. Telfast)
Fexofenadine is a substrate of various transporters (including P‑glycoprotein). CBD may influence transporter activity, which creates a theoretical interaction potential with respect to CBD metabolism and drug transport.
In practice, fexofenadine is considered minimally sedating, and many people tolerate it well. Still, if you use CBD together with fexofenadine:
- Be cautious with very high CBD doses
- Pay attention if you are also taking other medicines that may interact via CYP3A4 or transporters
- Monitor for unexpected side effects such as dizziness or unusual fatigue
CBD and diphenhydramine/dimetindene (1st generation; e.g. Betadorm, Fenistil)
Diphenhydramine and dimetindene are strongly sedating H1 blockers with anticholinergic effects (e.g. dry mouth, constipation, visual disturbances). When combined with CBD, marked additional tiredness is possible; this can significantly impair the ability to drive or operate machinery safely.
If a combination of CBD with 1st generation antihistamines cannot be avoided:
- Only use under medical supervision
- Keep doses as low as possible
- Avoid driving, cycling in traffic or working with machinery
Loratadine and fexofenadine are often regarded as more cautious options to combine with CBD. With cetirizine, potential additional tiredness is particularly relevant. Combining CBD with strongly sedating 1st generation antihistamines such as diphenhydramine is usually better avoided or should only be done with medical supervision.
How to use CBD with antihistamines safely
If you and your doctor decide that trying CBD with an antihistamine is appropriate, a careful approach can help reduce risks related to CBD drug interactions and drowsiness.
- Start low, go slow: begin with 5–10 mg CBD per day and increase gradually after 3–7 days, depending on tolerance and need.
- Timing: first test any new CBD and antihistamine combination in the evening. Avoid taking it for the first time before driving or important tasks.
- Monitor your symptoms: keep a brief diary and note tiredness/drowsiness, dizziness, dry mouth, palpitations or gastrointestinal issues.
- Avoid alcohol: alcohol can intensify drowsiness and further reduce your ability to drive or operate machinery safely.
- Be cautious with spacing doses: taking CBD and medicines at different times does not reliably prevent enzyme‑related interactions, as CBD’s effects on liver enzymes can last for several hours.
- Product quality: choose tested CBD products; check laboratory reports/COAs and start with clearly labelled concentrations.
Side effects of CBD and antihistamines: what can add up
Both CBD and antihistamines can cause side effects. When they are taken together, some of these effects may add up.
- CBD: tiredness, dry mouth, dizziness, occasionally a drop in blood pressure, gastrointestinal complaints (e.g. nausea, diarrhoea).
- Antihistamines: depending on the generation, sleepiness/drowsiness, dry mouth, headaches, occasionally stomach problems.
- Possible additive effects: increased tiredness/drowsiness, dry mouth, constipation, dizziness. With 1st generation antihistamines there may also be stronger anticholinergic effects (e.g. visual disturbances, urinary retention in predisposed individuals).
Who should be especially careful with CBD and allergy tablets?
Certain groups have a higher risk of CBD drug interactions or side effects when combining CBD with prescription medicines or over‑the‑counter antihistamines.
- Liver or kidney conditions: dose adjustments may be necessary; seek medical advice before combining CBD and antihistamines.
- Older adults: increased risk of falls due to sedation and blood pressure drops; use particularly cautious dosing and close monitoring.
- Pregnancy and breastfeeding: data on CBD safety are limited – clarify all use with a healthcare professional.
- Polypharmacy: the more medicines you take, the higher the potential for CBD CYP3A4 or other interactions; involve your doctor or pharmacist.
- Everyday life factors: during hay fever season, if you drive for work or have exams, first test CBD and antihistamine combinations in the evening and, if necessary, consider less sedating antihistamines with professional advice.
If you have pre‑existing liver or kidney disease, take several medicines, are pregnant or breastfeeding, or drive a lot, get medical advice before combining CBD with antihistamines and always first test the combination in the evening.
Complementary options for allergy treatment alongside CBD
Local allergy treatments such as nasal sprays (e.g. mometasone, azelastine) or eye drops act mainly at the site of application and usually have fewer systemic effects than oral antihistamines. This may reduce the likelihood of additive sedation with CBD. However, they can still have interactions or side effects, and the choice of treatment should always be discussed with your doctor or pharmacist.
💊 Medication Finder
We have analysed the interactions between CBD and 140 medications und Medikamentenarten analysiert. You can view the full overview here or use the search below to find your specific medication.
Before you add CBD to your treatment
If you are considering adding CBD to your antihistamine or allergy treatment, speak to your doctor or pharmacist beforehand. They can help you weigh up potential risks and benefits, review possible CBD interactions with your prescription medicines, choose suitable products and plan an appropriate dose.
Side effects of CBD
CBD (cannabidiol) is a naturally occurring substance derived from the hemp plant. Although CBD is generally considered well tolerated, side effects can occur. The most common include tiredness, dry mouth, dizziness, occasionally a temporary drop in blood pressure and gastrointestinal complaints (e.g. nausea or diarrhoea). The intensity and frequency vary between individuals.
Start with a low dose and observe how your body reacts. If symptoms persist, worsen or are severe, seek medical advice.
Side effects of antihistamines
Antihistamines are used to relieve allergy symptoms such as itching, a runny nose and sneezing. Common side effects – depending on the generation and active substance – include sleepiness/drowsiness, dry mouth, headaches or stomach discomfort. Modern 2nd generation antihistamines are generally less sedating, while older 1st generation substances more often cause tiredness and anticholinergic effects. If you notice anything unusual, contact a healthcare professional.
Dos & don’ts when combining CBD and antihistamines
- ✅ Start low with CBD (around 5–10 mg per day), test in the evening, and document your tolerance.
- ✅ Involve your doctor or pharmacist, especially if you have pre‑existing conditions or take other medicines.
- ❌ Do not combine CBD with strongly sedating antihistamines (e.g. diphenhydramine) without medical advice.
- ❌ Do not drive or operate machinery while you are unsure how the combination affects you.
- ❌ Avoid drinking alcohol at the same time as CBD and antihistamines.
Doctor’s checklist for your appointment
To discuss CBD and antihistamines safely with your healthcare professional, it helps to prepare the following:
- A list of all medicines and supplements including doses (also over‑the‑counter products and food supplements).
- Recent liver or kidney results (if available), information on pre‑existing conditions, pregnancy or breastfeeding.
- Everyday factors such as driving for work, shift work or upcoming exams.
- Any previous side effects when taking antihistamines and/or CBD.
💊 Medication Finder
We have analysed the interactions between CBD and 140 medications und Medikamentenarten analysiert. You can view the full overview here or use the search below to find your specific medication.
Conclusion: CBD and antihistamines (Claritin, Lorano, Zyrtec, cetirizine)
CBD can be combined cautiously with many antihistamines such as loratadine (Claritin, Lorano), cetirizine (Zyrtec) or fexofenadine. The key points are the choice of active substance (2nd generation is usually preferable), low starting doses of CBD, testing new combinations in the evening and monitoring for possible tiredness or dizziness. With strongly sedating 1st generation antihistamines such as diphenhydramine, particular caution or avoidance is advisable because of the higher risk of drowsiness and anticholinergic side effects. If you are unsure, or if you take several medicines, seek medical advice before combining CBD with allergy tablets.
Disclaimer: This article is for information purposes only and does not replace medical advice. Do not change medicines or dosages without consulting your doctor. No claims are made regarding the treatment or cure of illnesses.