ZzzQuil Nighttime Sleep Aid Review

I recently tried the ZzzQuil liquicaps nighttime sleep aid for several nights to see if it would help me sleep better.

It’s made by the company Procter & Gamble under their Vicks brand. It’s available online and over the counter in the United States, which is where I bought mine.

The main ingredient of the ZzzQuil I took is the antihistamine diphenhydramine HCL, which is also used in other sleep aids I’ve tried, such as Nytol One-A-Night.

Note that the ZzzQuil Nighttime Sleep Aid is not the same as ZzzQuil Pure Zzzs. The version I’m talking about in this article contains diphenhydramine, whereas ZzzQuil Pure Zzzs contains melatonin and herbal ingredients instead.

I’ll refer to the one I took just as ZzzQuil in this article.

My experience

In the photo below, you can see one of the liquicaps of ZzzQuil from the box I bought:

Night 1

I took just one ZzzQuil liquicap to test it on the first night. The instructions on the box were to take two liquicaps, but I wanted to see how I would feel with less the first time I took it. The liquicap is smaller and smoother than the standard white pills that many brands use, so it’s a bit easier to swallow.

I’d actually tried to go to sleep naturally at first, but was struggling to sleep because of the summer heat. So after tossing and turning for a while, I took the ZzzQuil and tried to fall asleep again. Interestingly, my sleep tracker data for that night showed that I was in and out of light sleep until around 30 minutes after taking it.

After that, I slept straight through the night without any wakings that I could remember. I apparently got 7 hours 20 minutes of sleep, which was the first time I’d managed over 7 hours in a couple of weeks.

Fuzzy head in the morning

When I woke up, I had a slightly fuzzy head. It wasn’t too bad though, and I felt back to normal around an hour later. I’ve had this kind of side effect from antihistamine sleep aids in the past, but it was tolerable since it was mild and short-lived.

Night 2

I decided to take the recommended dose of two liquicaps this time and then lay in bed reading to see if I noticed a sedative effect.

I didn’t feel particularly drowsy while reading, but I perhaps felt a little sleepy after around 40 minutes, so turned the light off to go to sleep. I had a couple of wakings in the night, but they were only a few minutes long. So again, it was a relatively good night’s sleep.

My sleep tracker also recorded that I got more REM and deep sleep than normal. Although I always take a sleep tracker’s sleep stages data with a pinch of salt because they aren’t 100% reliable, it’s still interesting that it showed more time spent in those restorative stages of sleep.

Cloudy head in the morning

Compared to the mild fuzzy head of the previous morning, I had a much cloudier head on the morning after the second night of trying ZzzQuil. Whether it was because I took the full dose this time, two nights in a row taking it, or something unrelated, I’ll never know.

What I do know is that I woke up with a headache, a heavy feeling in my eyes, and a cloudiness to my thinking that took a couple of hours to completely disappear.

Night 3

I took the full dose again and had a very similar experience as the second night. I woke up several times randomly in the night, but only for a few minutes each time.

I had a noticeably cloudy head in the morning again, which took a couple of hours to disappear completely.

Night 4

I decided to try just the single dose again on the final night. I didn’t sleep as well as the previous nights, taking a little longer to go to sleep, and waking up for longer periods in the night. I had a slightly foggy head in the morning, but not as much as I did after nights two and three.

Conclusion

Both my manual sleep diary and sleep tracker suggest that I had more total sleep on the nights I took the ZzzQuil. They also show that I had less wakings in the night compared to the week before, and appeared to fall back to sleep quicker after waking up in the night.

Comparatively, taking two liquicaps may have led to shorter wakings than when I took the half dose. However, I also experienced more side effects in the morning after taking the standard adult dose of two liquicaps. The cloudy head and headache were not pleasant, and took a while to clear.

The problem, as always when I try a new over the counter sleep aid, is that I don’t know how much can be put down to the effects of the ZzzQuil, how much was a placebo effect, and how much was down to other factors that I’m unaware of.

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Further information

ZzzQuil Ingredients

Please keep in mind that I bought the ZzzQuil in 2018, and the manufacturer may change the ingredients and other information over time.

Active ingredient

There was one active ingredient listed on the pack I bought:

• Diphenhydramine HCL 25 mg

Inactive ingredients

• FD&C Blue No. 1
• FD&C Red No. 40
• Gelatin
• Glycerin
• Pharmaceutical ink
• Polyethylene glycol
• Purified water
• Sorbitol sorbitan solution

Warnings and potential side effects

It’s always wise to check with your doctor or a qualified healthcare provider that a sleep aid is safe and appropriate for you to take, even if it’s available over the counter. They can give you personalised advice rather than relying on the brief description on a box or label.

When I took ZzzQuil, it didn’t come with an extensive user leaflet, but there were some important warnings on the back of the box. I won’t list them here because they may change over time. Again, it’s important to check with your healthcare provider if the antihistamine Diphenhydramine HCL is an appropriate choice for you.

As for side effects, the box I had didn’t list any, but other sources do discuss the potential side effects of Diphenhydramine HCL. You can find out about these through your doctor or pharmacist, and also check some medical websites. I’ll link to a few to get you started in the further reading section below.

Further reading

ZzzQuil.com – it has an FAQ section about their sleep aids.

WebMD – it has an extensive section on diphenhydramine HCL, including uses, side effects, interaction, and precautions.

NHS – the UK healthcare service website with an overview of diphenhydramine

Drugs.com – it has a section on taking diphenhydramine for sleep, and precautions for who should not use it.

Mayo Clinic – Q&A page on using antihistamines for sleep.

Research study in 2017 – researchers at the University of Pittsburgh published a study about the use of ‘potentially inappropriate’ antihistamines by older adults.

Sleep hygiene tips – my article discussing lifestyle choices and daily activities for sleep.