Dr.pharmacist
ZzzQuil

ZzzQuil

diphenhydramine

OTC DrugZzzQuil
Reviewed by Younghun Cho

Pharmacist's Verdict

ZzzQuil is an effective over-the-counter option for occasional sleeplessness, but it's essentially a rebranded allergy medicine (Benadryl) that can cause significant next-day grogginess and is not suitable for chronic insomnia.

Ingredient Analysis

Diphenhydramine Hydrochloride

Pros & Cons

Pros

  • Works quickly to help you fall asleep, usually within 30 minutes.
  • Readily available in most pharmacies and grocery stores without a prescription.
  • Effective for short-term sleep disruption, such as from travel or a temporary cold.

Cons

  • Commonly causes a 'hangover effect' with next-day drowsiness, fogginess, and dizziness.
  • The body builds tolerance quickly, making it less effective if used for more than a few nights in a row.
  • Can cause side effects like dry mouth, blurred vision, and constipation.
  • Not recommended for adults over 65 due to an increased risk of confusion and falls.
  • The active ingredient is simply diphenhydramine, which can be purchased for less money as generic allergy medication.

Safety Information

Warnings

Warnings Do not use for children under 12 years of age with any other product containing diphenhydramine, even one used on skin

Is ZzzQuil safe for you?

See pregnancy, interactions, and common concerns answered in our pharmacist safety FAQ.

Read safety review →

References

  1. 1.
    FDA Drug Label — Childrens Allergy Relief

    FDA DailyMed: Childrens Allergy Relief · FDA

  2. 2.
    FDA Drug Label — VICKS ZzzQuil NIGHTTIME SLEEP-AID Diphenhydramine HCl FREE OF

    FDA DailyMed: VICKS ZzzQuil NIGHTTIME SLEEP-AID Diphenhydramine HCl FREE OF · FDA

  3. 3.
    Insomnia in Elderly Patients: Recommendations for Pharmacological Management.

    Abad VC, Guilleminault C, Drugs & aging, 2018 · PubMed

  4. 4.
    Commonly prescribed medications and potential false-positive urine drug screens.

    Brahm NC, Yeager LL, Fox MD, et al., American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 2010 · PubMed

  5. 5.
    CAR/CSACI Practice Guidance for Contrast Media Hypersensitivity.

    Byrne A, Macdonald DB, Kirkpatrick IDC, et al., Canadian Association of Radiologists journal = Journal l'Association canadienne des radiologistes, 2025 · PubMed

  6. 6.
    Update on the treatment of chemotherapy and radiotherapy-induced buccal mucositis: a systematic review.

    Wen S, Brito L, Santander J, et al., Acta odontologica latinoamericana : AOL, 2023 · PubMed