Can I take Zyrtec (cetirizine) with Benadryl (diphenhydramine)?
Often, yes, you can take them together, but it’s usually not recommended unless a clinician tells you to. Both drugs treat allergy symptoms and both can cause drowsiness, so using both can increase side effects, especially sleepiness.
What happens if you take both? (side effects and risks)
The biggest concern is added sedation. Benadryl (diphenhydramine) is more likely to make people very sleepy, while Zyrtec (cetirizine) can also cause drowsiness in some people. Taking both may increase:
- Sleepiness or slowed reaction time
- Dizziness
- Dry mouth, constipation, or trouble urinating (more typical with Benadryl)
Is it ever safer to combine them?
Combining them may be considered in some situations, but it should be guided by a pharmacist or doctor. In many cases, clinicians instead recommend using one antihistamine and adjusting the timing rather than stacking two.
Which one should you use if symptoms are bad?
If you’re trying to avoid extra drowsiness, many people use Zyrtec (cetirizine) during the day and reserve Benadryl for short-term, more severe symptoms at night (because of its stronger sedating effect). Still, do not exceed labeled doses.
Who should avoid combining them?
Be especially cautious or ask a clinician first if you:
- Need to drive or operate machinery
- Have glaucoma, prostate/urination problems, or severe constipation (Benadryl can worsen these)
- Are older (higher risk of confusion and falls with sedating antihistamines)
- Have liver/kidney disease or take other sedating medications (sleep aids, opioids, some anxiety meds, alcohol)
Quick safety check
If you tell me your age, the reason you want to take them (hives, itching, runny nose, insect bite, etc.), and the doses you have, I can help you think through whether it’s likely to be a bad idea. If you have trouble breathing, swelling of the face/lips/tongue, or widespread hives, get emergency care.
Important note
I can’t confirm exact safety for your personal situation without your details. When in doubt, ask a pharmacist before taking both at once.
If you want, share the strengths on your labels (e.g., Zyrtec 10 mg, Benadryl 25 mg) and how many hours apart you were planning to take them.