When you catch a severe cold, you might consume some NyQuil before sleeping and not think much of it. However, some individuals utilize over-the-counter (OTC) sleep aids that contain antihistamines (specifically NyQuil) to help them fall asleep even when they’re not ill — a strategy that may not initially seem very risky, but can actually be more harmful than you realize.

If you need convincing, this anecdote from Whitney Cummings might just do the trick. On an episode of her podcast “Good For You,” the comedian disclosed that she had developed a habit of taking NyQuil before bedtime solely for the purpose of aiding her sleep. It was only after viewing security camera footage of her property (which she was utilizing to identify coyotes on her land – a typical problem in LA) that she became aware of the sinister effects.

The video revealed her walking into her yard in the middle of the night and urinating in some bushes. The most troubling aspect? She claimed to have no memory of this event taking place — and it all occurred after she had taken NyQuil. While Cummings found the situation amusing, she also acknowledged that it was somewhat frightening… and perhaps it was time to give up her nightly NyQuil habit. (Note: It’s unclear how much NyQuil Cummings consumed, but the recommended dosage for adults is 30 milliliters, or 2 tablespoons, every six hours, with a maximum of four doses in one day.)

How OTC Sleep Aids Function

Before delving into the topic, it’s crucial to establish the meaning of “OTC sleep aids.” There are natural OTC sleep aids, such as melatonin and valerian root, and then there are OTC sleep aids that contain antihistamines. The latter can be categorized as either pain-relieving or non-pain-relieving. The distinction lies in the fact that medications like NyQuil, AdvilPM, and Tylenol Cold and Cough Nighttime include pain relievers (such as acetaminophen or ibuprofen) to alleviate discomfort when one has a cold or flu, but they also contain antihistamines. On the other hand, medications marketed as “nighttime sleep aids,” for example, ZzzQuil, solely contain antihistamines.

Both types of antihistamine-containing OTC sleep aids take advantage of the drowsiness-inducing side effects associated with certain types of antihistamines, which are also used to combat allergies (consider Benadryl). As the name suggests, antihistamines counteract histamine, a chemical in your body that serves various functions — one of which is to keep your brain awake and alert.

So when histamine gets obstructed, you feel more fatigued, elucidates Ramzi Yacoub, Pharm.D., a apothecary and the principal pharmacy officer of RxSense. The most prevalent antihistamines discovered in OTC sleep aids are diphenhydramine (discovered in AdvilPM) and doxylamine (discovered in NyQuil and Tylenol Cold and Cough Nighttime), he supplements.

Adverse Reactions of OTC Sleep Aids with Antihistamines

Sleepwalking is a relatively well-documented side effect of prescription sleep medications like Ambien. While some may refer to Cummings’ experience as “sleepwalking,” that is not the most accurate way to describe the side effects explained by the comedian, according to Stephanie Stahl, M.D., a sleep medicine physician at Indiana University Health. She explains that while sleepwalking is not commonly reported with over-the-counter (OTC) sleep aids containing antihistamines, these medications can induce sedation, confusion, memory gaps, and disrupted sleep, all of which can heighten the risk of sleepwalking or nocturnal wandering.

This transient memory loss effect may also be recognized from another common substance: alcohol. This is because any sedative, including both alcohol and antihistamine-containing sleep aids, can lead to “disorders of confusional arousal,” as noted by Alex Dimitriu, M.D., founder of Menlo Park Psychiatry & Sleep Medicine, who specializes in psychiatry and sleep medicine. “Disorders of confusional arousal” refers to a state where individuals are in a semi-awake, semi-asleep condition and typically have difficulty recollecting what happened. When the brain is in this semi-asleep state, memory tends to be compromised.

Another possible (and ironic) side effect of certain antihistamine-containing OTC sleep aids is poor-quality sleep. Dr. Dimitriu explains that there are concerns that diphenhydramine, for example, may have a negative impact on sleep by reducing rapid eye movement (REM) sleep, commonly known as dream sleep. Lack of REM sleep can affect memory, mood, cognitive function, and even cellular regeneration, making this potential effect quite problematic.

Furthermore, OTC sleep aids containing antihistamines often do not actually promote longer sleep duration, according to Dr. Stahl. On average, individuals who take these medications only experience a minimal increase in sleep duration of approximately 10 minutes. Additionally, most people develop a tolerance and physical dependence within a few days of using these medications.

While antihistamine-containing OTC sleep aids are not classified as addictive substances, excessive use can lead to a dependence on them for sleep, warns Dr. Stahl. Over time, these medications may become less effective in improving sleep quality as the body develops tolerance, exacerbating the sleep problems. Therefore, while it may be acceptable to take a dose of NyQuil when feeling ill and experiencing difficulty sleeping, relying on antihistamine-containing OTC sleep aids solely for better sleep is unlikely to yield the desired outcome.

Other potential side effects of antihistamine-containing OTC sleep aids include dry mouth, constipation, blurred vision, as well as balance and coordination issues.

Furthermore, these medications have the potential to exacerbate additional health issues and disturbances in sleep patterns, such as the condition known as restless legs syndrome,” affirms Dr. Stahl.

And while antihistamines, in general, are a quite common medication, there can be potential drawbacks to taking them regularly in the long term. For instance, research published in JAMA Internal Medicine discovered that individuals who took a typical dosage of “first-generation antihistamines” (which can involve diphenhydramine — the one found in AdvilPM — among other types of antihistamines) approximately once per week over a 10-year span were at an increased risk of dementia. “Simply because something is accessible OTC does not imply that it is safe or effective,” expresses Dr. Stahl.

How to Determine If an Antihistamine-Containing OTC Sleep Aid Is Impacting Your Memory

One aspect that made Cummings’ story so terrifying was that it seems she’d never have discovered that it happened if she hadn’t checked her security camera. After all, not everybody has security camera coverage throughout their residence. Thankfully, though, there are some other intelligent ways to keep an eye on any unusual nighttime activity if you’re taking an antihistamine-containing OTC sleep aid.

“Applications that record sounds all night are the next best option to cameras for individuals who want to ensure they are not doing anything peculiar,” recommends Dr. Dimitriu. “Activity trackers and smartwatches may also provide indications of excessive activity at night,” he adds. Plus, most individuals grab their phones when they wake up, notes Dr. Dimitriu. So, examining texts, internet activity, and calls might also be beneficial, he says.

The Correct Approach to Consume Antihistamine-Containing OTC Sleep Aids

Experts concur that consuming an OTC antihistamine-containing sleep aid like NyQuil every night isn’t a terrific idea. But if you need assistance sleeping occasionally, here’s how to use OTC antihistamine-containing sleep aids safely.

Inform your doctor if you’re using them. One of the largest reasons to do this is because OTC antihistamine-containing sleep aids can interact with other substances you might commonly use — such as alcohol and marijuana, states Dr. Stahl. “They also interact with many other medications, including antidepressants,” she adds. “Before initiating any OTC medication, consult with your doctor to determine if it may interact with your other medications or worsen other medical problems and if a different treatment is preferable,” advises Dr. Stahl.

Absolutely avoid driving after taking them. “[OTC antihistamine-containing sleep aids] increase the risk of car accidents and may cause more driving impairment than a blood alcohol level of 0.1 percent,” explains Dr.

Stahl. Consequently, refrain from touching the steering wheel after consuming NyQuil. If you have worries about engaging in sleepwalking or experiencing memory loss similar to Cummings, kindly ensure that you place your keys in a secure location that is inaccessible until morning.

Do not depend on them for a long duration. Over-the-counter sleep aids containing antihistamines are designed to be used only occasionally when you’re feeling unwell and cannot sleep, states Yacoub. “If you are experiencing prolonged difficulty sleeping, I would advise you to consult your doctor who can further evaluate this,” he comments.

Follow good sleep practices. “This is ultimately what helps people achieve the best sleep, without relying on any medication,” says Dr. Dimitriu. Following regular bedtime and wake-up times, avoiding electronic screens before sleep, and getting sunlight in the morning can all greatly contribute to promoting good sleep practices, he notes.

If you’re dealing with insomnia, explore other treatments. “Instead of masking your sleep issues with medications, addressing the root cause is the most effective approach,” explains Dr. Stahl. “Cognitive-behavioral therapy for insomnia is the recommended primary treatment for persistent insomnia, rather than medication,” she adds.

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