A Guide to Over-the-Counter Sleep Aids: Benefits and Risks

The evidence supporting over-the-counter sleep aids is mixed and varies considerably by product type. Antihistamines like diphenhydramine and doxylamine are the most commonly used OTC sleep aids, found in brands like Benadryl, Unisom, and ZzzQuil. However, clinical practice guidelines from the American Academy of Sleep Medicine suggest against using diphenhydramine for chronic insomnia due to weak efficacy evidence—studies show it reduces sleep onset by only 7-11 minutes compared to placebo. [1] These medications carry significant risks including anticholinergic side effects (dry mouth, urinary retention, constipation), rapid tolerance development, cognitive impairment, and increased dementia risk with long-term use. [2]

Melatonin demonstrates modest but consistent benefits, reducing sleep onset latency by approximately 7 minutes and increasing total sleep time by 8 minutes in adults. [2-3] The effects appear more pronounced in older adults (≥55 years) with prolonged-release formulations and in children with neurodevelopmental disorders. [4-6] Melatonin has a favorable safety profile with minimal side effects (drowsiness, dizziness, headache) and low potential for dependence, though quality control issues exist with supplements. [2-3]

The information below provides a comprehensive review of common OTC sleep aids including brand names, dosing, efficacy evidence, and safety considerations. Antihistamines should be reserved for occasional short-term use only, while melatonin may be appropriate for certain populations, particularly older adults and those with circadian rhythm disorders. Neither should replace cognitive behavioral therapy for insomnia (CBT-I), which remains the first-line treatment for chronic insomnia.

A Guide to Over-the-Counter Sleep Aids: Benefits and Risks

Insomnia affects approximately one-third of adults worldwide, and many turn to over-the-counter (OTC) sleep aids for relief. While these products are widely available and perceived as safe alternatives to prescription medications, the evidence supporting their use varies considerably. This review examines the most common OTC sleep aids, their active ingredients, and what the research tells us about their effectiveness and safety.

Antihistamine-Based Sleep Aids

What the Evidence Shows

The efficacy data for antihistamine sleep aids is surprisingly limited. The American Academy of Sleep Medicine clinical practice guidelines suggest clinicians not use diphenhydramine for chronic insomnia, based on weak evidence of effectiveness. Studies show that diphenhydramine reduces sleep onset by an average of only 7-11 minutes compared to placebo, falling below the threshold for clinical significance. A 2022 network meta-analysis found that doxylamine demonstrated moderate efficacy for acute insomnia treatment, performing better than diphenhydramine in head-to-head comparisons.

Risks and Considerations

While antihistamines are generally well-tolerated in the short term, they carry several important risks:

Short-term side effects:

• Excessive daytime sedation and “hangover” effect
• Anticholinergic effects: dry mouth, constipation, urinary retention, blurred vision
• Cognitive and psychomotor impairment
• Paradoxical agitation in some individuals
• Worsening of restless legs syndrome

Long-term concerns:

• Rapid tolerance development (often within days to weeks)
• Increased risk of dementia with chronic anticholinergic medication use
• Rebound insomnia upon discontinuation
• Falls and injuries, particularly in older adults

Contraindications:

• Glaucoma
• Enlarged prostate with urinary difficulties
• Chronic obstructive pulmonary disease or asthma
• Pregnancy and breastfeeding (consult healthcare provider)
• Children under 12 years

Antihistamines are intended for occasional use only, not chronic insomnia. Older adults should be particularly cautious, as they are more susceptible to anticholinergic side effects and cognitive impairment.

Melatonin

What the Evidence Shows

Melatonin’s effectiveness varies by population and formulation. Meta-analyses show that melatonin reduces sleep onset latency by approximately 7 minutes and increases total sleep time by about 8 minutes in adults with primary insomnia—modest but statistically significant improvements. The effects appear more pronounced in certain populations:

• Older adults (≥55 years): Prolonged-release melatonin shows larger effect sizes for sleep efficiency
• Children and adolescents: More robust evidence for effectiveness, particularly in those with neurodevelopmental disorders
• Delayed sleep phase syndrome: Strong evidence for effectiveness in shifting sleep timing
• Jet lag and shift work: Some evidence for circadian rhythm adjustment

Importantly, melatonin appears to have minimal effect on sleep maintenance (staying asleep) and primarily helps with sleep onset.

Risks and Considerations

Melatonin has a favorable safety profile compared to other sleep aids:

Common side effects:

• Daytime drowsiness
• Dizziness
• Headache
• Nausea
• Vivid dreams or nightmares

Important considerations:

• Quality and dosing inconsistencies: Studies have found that actual melatonin content in supplements can vary widely from labeled amounts
• Drug interactions: May interact with blood thinners, immunosuppressants, diabetes medications, and birth control pills
• Not regulated as strictly as medications by the FDA
• Long-term safety data in adults is limited
• Effects on fertility and pregnancy are not well established

Melatonin has low potential for abuse or dependence and does not appear to cause tolerance with continued use, making it a reasonable option for short-term use in appropriate populations.

Combination Products

Many OTC sleep aids combine antihistamines with pain relievers:

• Tylenol PM: Acetaminophen + diphenhydramine
• Advil PM: Ibuprofen + diphenhydramine
• Excedrin PM: Acetaminophen + aspirin (in some formulations) + diphenhydramine

These products are marketed for people with pain that interferes with sleep. However, regular use of pain relievers when pain is not present carries risks of liver damage (acetaminophen) or gastrointestinal bleeding and cardiovascular effects (aspirin and ibuprofen). These combination products should only be used when both pain relief and sleep assistance are needed.

Herbal Supplements

Various herbal products are marketed for sleep, including valerian root, chamomile, lavender, passionflower, and lemon balm. While some studies suggest potential benefits, particularly for valerian, the evidence is generally inconsistent and limited by small sample sizes and methodological issues. Quality control is also a concern with herbal supplements, as active ingredient content can vary significantly between products.

The Bottom Line

Over-the-counter sleep aids offer varying levels of effectiveness with different risk profiles:

Antihistamines (diphenhydramine, doxylamine):

• Widely available but limited efficacy evidence
• Best reserved for occasional, short-term use (a few days to weeks)
• Significant anticholinergic side effects and dementia risk with chronic use
• Not recommended for older adults or chronic insomnia

Melatonin:

• Modest effectiveness for sleep onset, particularly in older adults and those with circadian rhythm disorders
• Favorable safety profile with low risk of serious side effects
• Minimal potential for dependence or tolerance
• Quality and dosing consistency concerns with supplements

General recommendations:

• OTC sleep aids should not replace good sleep hygiene practices
• Chronic insomnia (lasting more than 2 weeks) warrants medical evaluation
• Cognitive behavioral therapy for insomnia (CBT-I) is the first-line treatment for chronic insomnia
• Consult a healthcare provider before using sleep aids regularly, especially if you have medical conditions or take other medications
• Avoid alcohol when using any sleep aid
• Use the lowest effective dose for the shortest duration necessary

If insomnia persists despite OTC interventions and sleep hygiene improvements, professional evaluation is essential to identify underlying causes and explore evidence-based treatment options.

References

1. Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults: An American Academy of Sleep Medicine Clinical Practice Guideline. Journal of Clinical Sleep Medicine. 2017. Sateia MJ, Buysse DJ, Krystal AD, Neubauer DN, Heald JL.
2. Management of Insomnia. The New England Journal of Medicine. 2024. Morin CM, Buysse DJ.
3. Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PloS One. 2013. Ferracioli-Oda E, Qawasmi A, Bloch MH.
4. Efficacy of Melatonin for Chronic Insomnia: Systematic Reviews and Meta-Analyses. Sleep Medicine Reviews. 2022. Choi K, Lee YJ, Park S, Je NK, Suh HS.
5. Efficacy of Melatonin and Ramelteon for the Acute and Long-Term Management of Insomnia Disorder in Adults: A Systematic Review and Meta-Analysis. Journal of Sleep Research. 2023. Maruani J, Reynaud E, Chambe J, et al.
6. Efficacy on Sleep Parameters and Tolerability of Melatonin in Individuals With Sleep or Mental Disorders: A Systematic Review and Meta-Analysis. Neuroscience and Biobehavioral Reviews. 2022. Salanitro M, Wrigley T, Ghabra H, et al.