You should not take Zyrtec (cetirizine) together with Benadryl (diphenhydramine) together unless prescribed by your doctor as taking both will likely result in additive side effects, including:
- Dry mouth
- Dry eyes
- Difficulty urinating
- Blurred vision
- Fast heartbeat
Now there may be situations where it okay to take Benadryl and Zyrtec together upon the advice from your doctor. These situations include:
- Taking Benadryl for an allergic reaction
- Taking Benadryl at night as a sleep aid
Taking Benadryl With Zyrtec For An Allergic Reaction
Zyrtec is typically taken on a daily basis for the prevention of allergies. However, if you are having an allergic reaction (to a bee sting for example), Benadryl may be recommended to take as most studies show that is more effective than other antihistamines in reducing swelling and hives. Therefore, if you take Zyrtec daily, your doctor may recommend to take Benadryl only as needed for allergic reactions.
Taking Benadryl With Zyrtec For Insomnia
Benadryl, as a sedating antihistamine, is a commonly used as a night time sleep aid. In fact, diphenhydramine, the active ingredient in Benadryl is included in Tylenol PM and ZzzQuil, popular over the counter products for sleep. For short term use, your doctor may recommend taking Zyrtec in the morning and Benadryl in the evening for temporary treatment of insomnia.
If you do end up taking Benadryl and Zyrtec during the same day, be aware of the additive side effects discussed above. While daily use of both is not recommended, intermittent use together shouldn't cause too many problems.