Can You Take Zyrtec and Benadryl Together?
Short answer
MinorUsually not. Zyrtec (cetirizine) and Benadryl (diphenhydramine) are both antihistamines, so taking them together mostly adds side effects like drowsiness and dry mouth without much extra allergy relief. Doctors sometimes combine antihistamines on purpose, for example for hives, but that should be their call. For a severe allergic reaction with trouble breathing or throat swelling, antihistamines are not enough: use epinephrine if prescribed and call 911.
How the two are different
| Zyrtec (cetirizine) | Benadryl (diphenhydramine) | |
|---|---|---|
| Generation | Second generation | First generation |
| Drowsiness | Some people | Marked drowsiness is common |
| How long it lasts | About 24 hours | About 4 to 6 hours |
| Typical use | Daily allergy control | Short-term relief, sleep aids |
The Zyrtec label warns that drowsiness may occur and that alcohol, sedatives and tranquilizers can increase it. Benadryl causes more drowsiness and also has anticholinergic effects like dry mouth, constipation and trouble urinating.
Why combining them is rarely worth it
Both medicines block the same histamine receptor. Once it is blocked, adding a second antihistamine does little for sneezing or itching, but the drowsiness adds up. That can affect driving, work and balance, and it raises fall risk in older adults. The American Geriatrics Society lists diphenhydramine among medicines older adults should generally avoid.
Hidden diphenhydramine
The Benadryl label says not to use it with any other product containing diphenhydramine, even one used on the skin. It is in many products that do not say Benadryl on the front:
- Sleep aids: ZzzQuil, Unisom SleepGels, store-brand sleep aids
- “PM” pain relievers: Tylenol PM, Advil PM, Aleve PM
- Some nighttime cold and allergy products
- Anti-itch creams and sprays
Better options
- For daily allergies, pick one non-drowsy antihistamine (Zyrtec, Claritin or Allegra) and take it every day during your season.
- If one is not enough, a steroid nasal spray is often more effective than adding a second pill. Ask a pharmacist.
- If Zyrtec makes you sleepy, try taking it in the evening.
What the FDA labels say
This interaction is based on how the two medicines work rather than a specific warning printed on either label.
Frequently asked questions
How long after Benadryl can I take Zyrtec?
Benadryl’s effects usually last 4 to 6 hours. If you want to switch to daily Zyrtec, starting it after Benadryl has worn off avoids stacking drowsiness. A pharmacist can help you plan the switch.
Can I take Zyrtec in the morning and Benadryl at night?
Some doctors recommend this for hives or allergies that disturb sleep. Because Zyrtec lasts 24 hours, there is still some overlap, so ask your doctor first, especially if you are older or take other sedating medicines.
Which is better for allergies, Zyrtec or Benadryl?
For ongoing allergies, Zyrtec is usually better: it lasts all day and causes less drowsiness. Benadryl works quickly but wears off sooner and is more sedating.
Taking anything else?
Add all your medicines, supplements and alcohol to check every combination at once.
Sources
This page is for general education and is based on FDA labeling. It is not medical advice and does not replace a conversation with your doctor or pharmacist, who know your health history, doses and other medicines. If you think you have taken too much of a medicine, call Poison Control at 1-800-222-1222 or 911.