Can You Take Benadryl After Taking Allegra The Same Day?

Hi Kim and thank you for your great question. Let's get right into it!

Let's first go over each drug in question here.

What Is Allegra

Allegra (fexofenadine) is a “second generation” antihistamine. It works by binding to histamine receptors in the body so that histamine can’t bind to them.

This helps to reduce the symptoms typically caused by allergies. It is often portrayed as “non-drowsy” but it typically causes drowsiness in about 10-15% of people that take it.

It is generally well-tolerated and lasts about 24 hours.

What Is Benadryl

Benadryl (diphenhydramine) is a “first generation” antihistamine. It commonly causes drowsiness and can also cause dizziness, dry mouth, constipation, urinary retention, and next-day fatigue.

It also works by binding to histamine receptors, but binds to many more in the central nervous system (in your brain) compared to fexofenadine. This is what causes the drowsiness and dryness seen with diphenhydramine.

Taking Both Together

Since fexofenadine and diphenhydramine are both antihistamines, it’s not routinely recommended to take them together.

They are both working to do the same thing. Specifically, in your case, fexofenadine taken at 2 pm will still be blocking most of the histamine receptors in your body when you plan to take the diphenhydramine, 8 hours later. Fexofenadine typically lasts 24 hours.

There are rare instances, where using diphenhydramine a few hours after fexofenadine may be appropriate.

If you were to begin to suffer from an acute allergic reaction, then taking Benadryl might be useful. Aside from this instance, please don’t take both unless your physician or another healthcare professional directs you to.

Lastly, if you are regularly using diphenhydramine to help you fall asleep, it is not an effective long-term strategy. It hasn’t been shown to help with sleep quality beyond a few nights.

Also, recently, long-term use has been linked to developing dementia later in life.

If you find that your sleep quality isn’t the best, it might be a good time to reevaluate your sleep hygiene. There’s a lot involved in sleep hygiene, and I will link you to a good resource if you’d like to read up on it more.

From personal experience, I know that making sure that I don’t use my phone or watch any TV for an hour or so before bedtime helps.

Bright lights like phones and your TV cause your brain to think that it’s daytime, so you tend to have a more difficult time falling asleep. Instead, I try to read a bit to decompress before I fall asleep.

There’s always something that can be done to improve your sleep hygiene. I would encourage you to read up on it a bit and give it a try.