Sleep Disorders Treatment Doxylamine in Unisom and Nyquil Not Recommended for Insomnia Treatment Drug Causes Sleepiness With Potential Tolerance and Other Side Effects By Brandon Peters, MD Brandon Peters, MD Facebook Twitter Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist. Learn about our editorial process Updated on November 11, 2021 Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Sanja Jelic, MD Medically reviewed by Sanja Jelic, MD Sanja Jelic, MD is board-certified in pulmonary disease, sleep medicine, critical care medicine, and internal medicine. She is an assistant professor and attending physician at Columbia University College of Physicians and Surgeons in New York, NY. Learn about our Medical Expert Board Print Table of Contents View All Table of Contents Uses Before Taking Contraindications Side Effects Frequently Asked Questions Doxylamine is a sleep aid in products like Unisom and Nyquil that you can buy over the counter. Some people take it to treat insomnia. Insomnia is a sleep disorder where you have trouble falling asleep or staying asleep. You don't need a prescription for doxylamine. That doesn't mean the medicine doesn't come with potential side effects, though. Before taking doxylamine, learn the possible risks. This article goes over how doxylamine works, its uses, and what problems it can cause. Verywell / Jessica Olah Uses Doxylamine is an antihistamine, a type of medication often used to treat allergies. It can also reduce nighttime cold symptoms. One of its side effects is drowsiness. This effect can help some people who have trouble getting to sleep or staying asleep, so doxylamine is often used in over-the-counter sleep aids. But note that it shouldn't be used to treat insomnia. Like many sleeping pills, doxylamine affects neurotransmitters. These are chemical messengers that send signals between brain and nerve cells (neurons). Doxylamine blocks receptors that let the chemical histamine stimulate neurons. This causes you to get sleepy. Doxylamine works centrally (within the central nervous system) and elsewhere in the body to sedate you. Before Taking Doxylamine is an over-the-counter medication. For that reason, risks might be slightly lower than with prescription medications that need careful monitoring. No routine tests are recommended with its use. Ultimately, doxylamine is not the best option if you are considering taking sleeping pills. There are other choices that are better for aiding sleep. Doxylamine doesn't promote sleep in the same way as prescription sleep medications, such as benzodiazepine and non-benzodiazepine medications. To take a medication for its side effect—in this case, sleepiness—is not recommended. Doxylamine is a non-habit forming medication. However, you can develop a tolerance to it, which means you'll have to take more of it over time to get the same effect. This can lead to an increased risk of other side effects. Precautions and Contraindications Certain groups of people shouldn't take doxylamine. Age Restrictions Children under 12 years of age shouldn't use doxylamine 25 milligrams (mg). Children under 6 and elderly people shouldn't use it without a healthcare provider's advice. Breastfeeding According to the National Institutes of Health, taking small, occasional doses while nursing shouldn't cause problems for the baby. However, larger doses or long-term use may cause drowsiness, irritability, and colicky symptoms in breastfed babies. It may also lower your milk supply. Medical Conditions People with many conditions should be cautious about doxylamine as it may cause problems or drug interactions. These conditions include: Glaucoma Hyperthyroidism Heart disease High blood pressure (hypertension) Asthma Chronic obstructive pulmonary disease (COPD) Pneumonia Peptic ulcer disease Prostate enlargement Liver disease Bowel or bladder obstruction If you're concerned about whether you may have problems using doxylamine, you should first consult with your healthcare provider. Negative drug interactions are also a risk, especially with other medications that affect the brain, so be sure to review your medications with your healthcare provider or pharmacist before starting to use doxylamine. Side Effects The list of potential side effects for any drug can be quite long, and doxylamine is no exception. Although you likely wouldn't experience most side effects, and may not have any at all, some that occur commonly with doxylamine include: DizzinessLoss of coordinationHeadacheStomach painDry mouth or noseConstipationDifficulty urinatingBlurred or double vision Potential Serious Reactions While they're rare, serious side effects can result from the use of doxylamine, including: Severe allergic reaction (anaphylaxis), including difficulty breathing Low blood cell counts (agranulocytosis, anemia, thrombocytopenia, and leukopenia) Abnormal heart rhythms or altered heart rate Seizures Toxic psychosis Inner ear problems (acute labyrinthitis) Hallucinations Confusion or delirium Low blood pressure Insomnia Healthcare Provider Discussion Guide Get our printable guide for your next healthcare provider's appointment to help you ask the right questions. Download PDF Email the Guide Send to yourself or a loved one. Sign Up This Doctor Discussion Guide has been sent to {{form.email}}. There was an error. Please try again. Summary Doxylamine is an antihistamine drug that is often used in over-the-counter medications to promote sleep. Side effects can range from dizziness and headaches to confusion and serious allergic reactions. People with certain medical conditions like glaucoma and heart disease should not take doxylamine. If you want to try it to help with insomnia, talk to your healthcare provider first. A Word From Verywell If you experience any difficulties when taking this drug, you should be in close contact with your primary healthcare provider. If you wish to pursue other preferred treatments for insomnia, you should likewise make an appointment and discuss the better prescription options that are available. Effective treatment may include medications, learning better sleep habits, or cognitive behavioral therapy for insomnia (CBTI). Frequently Asked Questions Can I take Unisom every night? No. Unisom is intended as a temporary sleep aid and should not be taken for more than two weeks. If you need ongoing help falling asleep, speak to your healthcare provider. Learn More: What Causes Insomnia? Does Unisom help with morning sickness? Yes. The doxylamine succinate in Unisom taken with vitamin B6 can treat morning sickness during pregnancy. Talk to your healthcare provider before taking the combination to be sure it’s right for you. Learn More: Using Doxylamine Safely in Pregnancy Why is doxylamine not recommended for older adults? Doxylamine may increase the risk for dementia. This is due to its anticholinergic properties, which means it blocks neurotransmitters that transmit messages along the nervous system. According to researchers, anticholinergic medications are associated with cognitive decline. Was this page helpful? Thanks for your feedback! Tossing and turning night over night can have a big impact on your quality of life. Our free guide can help you get the rest you need. Sign up for our newsletter and get it free. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 6 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Krystal AD, Richelson E, Roth T. Review of the histamine system and the clinical effects of Hi antagonists: basis for a noew model for understanding the effects of insomnia medications. Sleep Med Rev. 2013;17(4):263-272. doi:10.1016/j.smrv.2012.08.001 National Library of Medicine (US). Drugs and Lactation Database. Doxylamine. MedlinePlus. Doxylamine. Unisom. Frequently Asked Questions. Koren G, Clark S, Hankins GDV, et al. Maternal safety of the delayed-release doxylamine and pyridoxine combination for nausea and vomiting of pregnancy; a randomized placebo controlled trial. BMC Pregnancy and Childbirth. 2015;15(1):59. Coupland CAC, Hill T, Dening T, Morriss R, Moore M, Hippisley-Cox J. Anticholinergic drug exposure and the risk of dementia: a nested case-control study. JAMA Intern Med. 2019;179(8):1084. doi:10.1001/jamainternmed.2019.0677