Can You Take Benadryl With Zyrtec?
In our latest question and answer, our pharmacist discusses whether or not Benadryl and Zyrtec can be taken together.
Can I take Benadryl and Zyrtec together? I find that only taking Zyrtec hasn't been helpful enough and want to add something else on to make my allergy symptoms go away.
Jul 11, 2022- Both Benadryl and Zyrtec are antihistamines that work the same way, so taking them together increases the risk of side effects like drowsiness, dry mouth, and dry eyes without providing added allergy relief. Taking both medications together generally isn't recommended unless your doctor approves it for specific situations like an acute allergic reaction or if Benadryl is being used as a short-term sleep aid. If Zyrtec alone isn't controlling your symptoms, talk to your doctor about alternative options rather than adding another antihistamine.
There are two main concerns with taking multiple drugs that work the same way (Zyrtec and Benadryl in this case):
- There is the risk of additive side effects. Both Zyrtec and Benadryl will cause you to be tired for example. The use of both together will only increase the chance of this happening and to a more severe degree.
- You likely won't experience much-added benefits. Taking two antihistamines won't make them work twice as well. I discuss this in more detail in the following paragraph.
As mentioned, both Benadryl and Zyrtec are antihistamines, and they both work the same way mechanistically. Specifically, they both block what is known as the 'histamine-1 receptor'. This prevents histamine from binding to these receptors and producing the symptoms we are all very familiar with (runny nose, sneezing, itching etc...).
Now, both do a pretty good job of blocking histamine receptors on their own. Taking both Benadryl and Zyrtec will simply cause them to compete for the same receptors. Once a receptor is blocked, it's blocked. In other words, if Benadryl is already bound to a histamine receptor, Zyrtec won't be able to act on it. This is why there isn't much of a cumulative effect in using two antihistamines at the same time.
So, the overall point here is that taking Benadryl and Zyrtec together doesn't increase the antihistamine effect of both, but will likely only increase the risk of side effects. These side effects include:
- Sedation (i.e. tiredness)
- Dry mouth
- Dry eyes
- Constipation
I said at the beginning of this answer that there are occasions where these drugs could be used together. These situations include:
- If you are experiencing an allergic reaction.
- You are using Benadryl as a sleep aid.
- You take Benadryl and Zyrtec on the same day but separated by an appropriate amount of time.
Situations Where You May Use Benadryl And Zyrtec Together
In many cases, Benadryl and Zyrtec shouldn't be taken together, and certainly not every day. However, the following sections detail situations where it may be beneficial to do so.
Allergic Reaction
Although studies are conflicting, some show that Benadryl is slightly more effective than Zyrtec at stemming an allergic reaction, such as the reaction some people have to bee stings. This may be because Benadryl has stronger 'anticholinergic' effects than Zyrtec.
The anticholinergic actions of Benadryl are responsible for many of the side effects, like sedation, but they also help to reduce itching and swelling. Zyrtec has been shown in studies to help reduce itching, but again, Benadryl may have the upper hand here. In fact, it is Benadryl, not Zyrtec, that is recommended in the guidelines for managing vaccine reactions for reducing hives and itching due to an adverse immunization reaction.
Let's say you take Zyrtec on a daily basis for your seasonal allergies and you found yourself in a situation where you were having an allergic reaction. Benadryl may be an appropriate choice to add on since it may help provide you with some additional relief.
Sleep Aid
Another situation where the combination may be okay is if your doctor recommends taking Benadryl as a short-term treatment for insomnia. The active ingredient in Benadryl is diphenhydramine, which is used in many over-the-counter sleep aids. It is the active ingredient in ZzzQuil and also the sleep aid used in Tylenol PM for example.
Your doctor may recommend taking Zyrtec in the morning, every day, to manage your allergy symptoms and Benadryl in the evening as needed. While this may make you slightly more tired than using Benadryl alone to sleep, this shouldn't be much of an issue because, after all, you are trying to go to bed.
Separate Administration Time
Benadryl is a short-acting, first-generation antihistamine. Each dose only lasts around four to six hours. Therefore, if you took Benadryl first, and then Zyrtec four to six hours later, Benadryl will have worn off by that point so there is no interaction to be concerned about.
Final Words
You mentioned in your question that Zyrtec wasn't helping enough for you. Adding on Benadryl, in my opinion, is not the best option for optimal allergy relief.
At the very least, be sure to discuss your concerns with your doctor. They can help you find the best therapy for your situation.
References & sources
Glossary — Terms in This Answer
- Antihistamines
- Medications that block the effects of histamine, a chemical in the body that causes allergy symptoms like itching and sneezing.
- Histamine-1 receptor
- A specific site on cells where histamine attaches to trigger allergy symptoms.
- Additive side effects
- When unwanted effects from two drugs combine and become stronger together than either drug alone.
- Sedation
- A state of drowsiness or reduced alertness caused by medication.
- Anticholinergic
- A medication property that blocks certain nerve signals and can reduce itching and swelling but may cause dry mouth and drowsiness.
- First-generation antihistamine
- An older type of antihistamine that easily enters the brain and typically causes drowsiness.
- Nasal steroid
- A spray medication containing a steroid that reduces inflammation in the nasal passages to relieve allergy symptoms.
- Immunization reaction
- An unwanted physical response the body has to a vaccine.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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