Nyquil Vs. ZzzQuil: What Is The Difference?

Hello and thank you for your question! There are a few differences between NyQuil and ZzzQuil that we are happy to discuss here.

They Contain Different Antihistamines

First and foremost, Nyquil & ZzzQuil contain sedating antihistamines, but different ones. ZzzQuil contains diphenhydramine, the active ingredient in Benadryl, while Nyquil contains doxylamine.

Both antihistamines cause sedation shortly after administration and help you to fall asleep.

Although NyQuil and ZzzQuil contain different sedating antihistamines (diphenhydramine vs. doxylamine), those antihistamines are very similar in terms of how quickly they work (around 30 minutes), how long they last (4 to 6 hours), and how potent they are.

Direct comparative studies and evaluations are limited, so it is difficult to say one is better than the other, but overall, they are quite comparable.  Individuals will vary in regard to which ingredient works best for them.

NyQuil Contains More Ingredients

In addition to the difference in antihistamines, Nyquil contains additional ingredients for the treatment of cough/cold symptoms.

ZzzQuil contains diphenhydramine as the only ingredient.  It is intended solely for use as a nighttime sleep aid.

NyQuil on the other hand contains additional ingredients:

• Acetaminophen (the active ingredient in Tylenol) for treating fever/pain.
• Dextromethorphan for suppressing cough.
• Doxylamine as mentioned above, for sedation. Sedating antihistamines may also help relieve a runny nose as well as cough due to post nasal drip.

Final Words

If you are only in need of something to assist in falling asleep, it's better to just stick with ZzzQuil. It will most likely do the job, without the extra ingredients and side effects you may experience from the additional ingredients contained in Nyquil.

Thanks again for your question and please feel free to reach out with any further questions in the future.