If I have a bad allergic reaction and I take Zyrtec on a regular basis, can I take a Benadryl for it to be more effective?
While it generally isn't recommended to take Benadryl (diphenhydramine) if you already take Zyrtec (cetirizine), there are exceptions, especially Benadryl is just used on an as needed, or acute basis.
Benadryl is one of the more effective antihistamines in reducing the inflammation and itching from allergic reactions. It is commonly thought that Benadryl is more effective than other antihistamines, like Claritin, when used to stem an allergic reaction but studies aren't conclusive.
Nevertheless, taking Benadryl if you already take a daily antihistamine like Zyrtec may provide more relief of symptoms from allergic reactions (e.g. for bee stings) and can be used if recommended by your doctor. It is important to note however that antihistamines are not a replacement for epinephrine during a severe allergic reaction/anaphylaxis.
Benadryl is also used commonly as a sleep aid. In fact, it is a common ingredient in over the counter products used to promote sleep like ZzzQuil. Your doctor may recommend taking Benadryl as needed in evening due to its sedative properties, even if you already take a daily antihistamine like Zyrtec.
While there may be situations where Benadryl is recommended to take after dosing with Zyrtec, there is an increased risk of additive side effects such as:
- Dry mouth
- Dry eyes
Since there is a risk of additive side effects, the combination of Benadryl and Zyrtec should not be used routinely, just as needed on an acute basis if your doctor recommends it to you.