Not on your own: Zyrtec (cetirizine) and Benadryl (diphenhydramine) are both antihistamines, and the NHS says not to take 2 antihistamines together unless a doctor recommends it. The NHS also says that for a severe, itchy skin rash, a doctor may advise 2 antihistamines for a few days: a non-drowsy one like cetirizine in the day and a drowsy one at night if the itching keeps you awake. Both labels warn that the medicine can make you drowsy, so ask a doctor or pharmacist before you add one to the other. Get emergency help right away if hives come with trouble breathing or swallowing, wheezing, swelling of the tongue or mouth, dizziness, or passing out.
What is in Zyrtec and Benadryl?
Each one has a single active ingredient, and both are listed on the Drug Facts label with the purpose "antihistamine". They are different drugs, but they are in the same class.
This page is about plain Zyrtec and plain Benadryl. Other versions and store brands can contain other ingredients or amounts, so check the Drug Facts on your own box.
- Zyrtec (Zyrtec Hives, per tablet): cetirizine HCl 10 mg, taken once a day. The label says not to take more than one 10 mg tablet in 24 hours
- Benadryl (per tablet): diphenhydramine HCl 25 mg. Adults and children 12 and over take 1 to 2 tablets every 4 to 6 hours, and no more than 6 times in 24 hours
- Shared: no ingredient, but the same type of drug, and both labels warn about drowsiness (Benadryl's says marked drowsiness may occur)
Why is taking both a problem?
The NHS says plainly: do not take 2 antihistamines together unless recommended by your doctor. The main concern you can feel is drowsiness. The Benadryl label says marked drowsiness may occur. The Zyrtec label says drowsiness may occur. The NHS notes that cetirizine is called non-drowsy but seems more likely to make you sleepy than loratadine or fexofenadine.
Both labels say alcohol, sedatives and tranquilizers may increase drowsiness, and both tell you to ask a doctor or pharmacist before use if you take sedatives or tranquilizers. Neither label names the other drug, and neither says the two can be taken together.
Both labels say to be careful driving or using machinery, and to avoid alcohol. If you have taken both, do not drive until you no longer feel sleepy.
When might a doctor tell me to take both?
The NHS describes 1 situation: sometimes doctors recommend that people with a severe, itchy skin rash take 2 different antihistamines together for a few days. As well as a non-drowsy antihistamine during the day, such as cetirizine, your doctor may advise a drowsy antihistamine at night if the itching makes it hard to sleep.
That is a short-term plan a doctor makes for you. It is not a reason to add Benadryl every time Zyrtec feels weak. If you already have that plan from a doctor, follow it. If you do not, ask a doctor or pharmacist before you add the second one.
The Zyrtec Hives label also says to stop and ask a doctor if hives do not improve after 3 days of treatment or last more than 6 weeks. Hives that last that long need a proper look, not a second pill.
Which other medicines already contain diphenhydramine?
The Benadryl label says not to use it with any other product that contains diphenhydramine, even one used on skin. That includes creams, gels or sprays with diphenhydramine, so check the label of anything you put on hives too.
Diphenhydramine is also the sleep ingredient in many PM pain relievers. If you are taking Zyrtec, these count as adding a second antihistamine, and you should not take them with Benadryl.
- Tylenol PM Extra Strength (per caplet): acetaminophen 500 mg (the drug in Tylenol) plus diphenhydramine HCl 25 mg
- Advil PM caplets (per caplet): ibuprofen 200 mg (the drug in Advil and Motrin) plus diphenhydramine citrate 38 mg
- Both PM labels: do not use with any other product containing diphenhydramine, even one used on skin, and do not use in children under 12
Can kids or older adults take Zyrtec and Benadryl together?
Do not combine them for a child unless your child's doctor tells you to. HealthyChildren.org, from the American Academy of Pediatrics, says some antihistamines can make children sleepy and can be toxic if taken in excess. It says not to give Benadryl to children younger than 6 unless your pediatrician advises it.
The Benadryl label says children under 6 should not use it, and not to use it to make a child sleepy. It also warns that excitability may occur, especially in children. The Zyrtec Hives label says children under 6 should ask a doctor.
For older adults, MedlinePlus says diphenhydramine generally should not be used except to manage serious allergic reactions. The Zyrtec Hives label says adults 65 and over should ask a doctor before use.
When should you get care?
In an emergency, call 911Call 911 if hives come with trouble breathing or swallowing, wheezing, swelling of the tongue or in or around the mouth, trouble speaking, drooling, dizziness, or passing out. The Zyrtec Hives label says to get emergency help immediately: these can be signs of anaphylaxis, which can happen when hives first appear or up to a few hours later. If a doctor prescribed you an epinephrine injector, follow the plan they gave you: the label says never to use Zyrtec in place of it.
Call 911 if someone who took these medicines collapses, has a seizure, has trouble breathing, or cannot be woken up.
Call Poison Help at 1-800-222-1222 if a child took either medicine by accident, or if you took more than the label allows.
See a doctor if hives do not improve after 3 days of treatment, last more than 6 weeks, or look bruised, blistered, an unusual color, or do not itch.
Stop Zyrtec and get medical help right away if you have an allergic reaction to it, as its label says.
How our AI doctor decides when to send you to care ›Who should ask a doctor or pharmacist before either one?
These come from the Zyrtec Hives and Benadryl labels. If you are pregnant, both labels say to ask a health professional first. If you are breastfeeding, the Benadryl label says to ask a health professional, and the Zyrtec Hives label says it is not recommended.
- Benadryl: glaucoma, a breathing problem such as emphysema or chronic bronchitis, or trouble urinating from an enlarged prostate
- Zyrtec: liver or kidney disease. Do not use it at all if you have had an allergic reaction to it or to any antihistamine that contains hydroxyzine
- Zyrtec Hives: hives that are an unusual color, look bruised or blistered, or do not itch
- Both: you take sedatives or tranquilizers
Common questions
Can I take Zyrtec and Benadryl together?
Not on your own. Both are antihistamines, and the NHS says not to take 2 antihistamines together unless your doctor recommends it. A doctor may advise a non-drowsy antihistamine in the day and a drowsy one at night for a few days for a severe, itchy rash, but that is their call to make.
How long after Zyrtec can I take Benadryl?
Neither label gives a spacing rule for switching between them. Zyrtec is a once-a-day dose, so taking Benadryl a few hours later is still taking 2 antihistamines the same day. Ask a doctor or pharmacist before adding Benadryl the same day. If a doctor already gave you a day-and-night plan, follow their timing.
I took Zyrtec and Benadryl by accident. What should I do?
Do not take any more of either, skip alcohol, and do not drive until you no longer feel sleepy. If you took more than the label dose of either one, or you are not sure, call Poison Help at 1-800-222-1222. Call 911 if someone has trouble breathing, has a seizure, collapses, or cannot be woken up.
Can I use Benadryl cream with Zyrtec?
The Benadryl tablet label says not to use it with any other product that contains diphenhydramine, even one used on skin. That rule is about diphenhydramine plus diphenhydramine. Whether a skin product is right for your rash alongside Zyrtec is a question for a pharmacist, so check the cream's label and ask.
Can I take Tylenol PM or Advil PM with Zyrtec?
Both contain diphenhydramine, the antihistamine in Benadryl, so taking one with Zyrtec means 2 antihistamines. Ask a doctor or pharmacist first. Never take Tylenol PM or Advil PM with Benadryl.
Is Zyrtec stronger than Benadryl?
They are not compared that way on the labels. Zyrtec is taken once a day, and Benadryl every 4 to 6 hours. The NHS calls cetirizine non-drowsy, though it says it can still make some people sleepy, while the Benadryl label warns that marked drowsiness may occur. If one is not helping, ask a doctor or pharmacist what to try next rather than stacking them.
Pymander is not a replacement for a physician and does not provide medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with questions about a medical condition. If you think you may have a medical emergency, call 911.