Diphenhydramine (Benadryl): What It Is and How It Relates to Motion Sickness
Educational summary · drug class: First-generation (sedating) antihistamine (H1-receptor antagonist with central anticholinergic activity) · last reviewed 2026-06-29
Diphenhydramine, sold over the counter in the US as Benadryl, is a first-generation (sedating) antihistamine. MedlinePlus notes that diphenhydramine 'is used to prevent and treat motion sickness.' Importantly, in the US the OTC Benadryl Drug Facts label lists only allergy and cold symptoms as its uses — motion sickness is not a labeled use, whereas dimenhydrinate (Dramamine) is an OTC antihistamine specifically labeled as an antiemetic. Diphenhydramine causes marked drowsiness, and whether it's appropriate for you is a question for your doctor or pharmacist.
Not medical advice. This page is for general educational and informational purposes only. It is not medical advice and is not a substitute for the advice of a qualified healthcare professional. Dizzout is not a medical provider — we are not doctors or pharmacists. The information here is a general summary drawn from sources such as the FDA-approved label and other public health resources, and it may not reflect the most current changes; the official product label is the authoritative source. Whether any medicine is right for you, and how much to take, are individual decisions that depend on your health, age, and other medicines. We do not provide dosing instructions — always read the product label and follow its directions. Talk to your doctor or pharmacist before starting, stopping, or changing any medication, and never disregard or delay professional medical advice because of something you read here. If you think you may have a medical emergency, contact a doctor or your local emergency number immediately.
What it is
Diphenhydramine is a first-generation, sedating antihistamine (an H1-receptor antagonist with anticholinergic activity). In the US it is best known over the counter as Benadryl, and it is also the sleep-aid ingredient in products such as some Unisom and ZzzQuil formulations. It is closely related to dimenhydrinate (Dramamine), the sedating antihistamine that in the US carries an OTC antiemetic indication for motion sickness. MedlinePlus lists diphenhydramine among the medicines 'used to prevent and treat motion sickness,' but the US OTC Drug Facts label for Benadryl itself covers hay-fever/upper-respiratory-allergy and common-cold symptoms rather than motion sickness — so if motion sickness is your goal, this is a use to discuss with a pharmacist rather than one printed on the box.
Availability: Sold over the counter in the US and many countries (e.g., Benadryl), but its OTC Drug Facts labeling covers allergy, cold, and sleep — not motion sickness. Availability, brands, and formulations vary by country. Legal status, brand names, and availability vary by country — check what applies where you live.
How it may help with motion sickness
Motion sickness happens when balance signals from the inner ear (vestibular system) conflict with what your eyes and body sense. First-generation antihistamines like diphenhydramine cross into the brain, and reference sources including the CDC Yellow Book attribute their anti-motion-sickness effect mainly to central anticholinergic action rather than to histamine blockade — dampening overactive inner-ear signaling and the brain's nausea and vomiting response. Such antihistamines are generally taken before travel to help prevent symptoms.
General timing
Because motion sickness is not a labeled use of OTC Benadryl in the US, the diphenhydramine Drug Facts label does not give motion-sickness timing or dosing. General references note that sedating antihistamines are taken before travel to help prevent symptoms rather than after they start. We do not provide dosing instructions — follow the directions on the product label and ask your doctor or pharmacist whether, and how, to use it for motion sickness.
We don't provide dosing instructions. The exact amount, schedule, and whether it suits you are individual decisions — read the product label and follow its directions, and ask a doctor or pharmacist.
Common side effects
Sources such as the product label commonly list:
- Drowsiness or marked sleepiness (the label warns marked drowsiness may occur)
- Dizziness
- Dry mouth, nose, and throat
- Headache
- Blurred vision
- Constipation or difficulty urinating
- Excitability or restlessness (a paradoxical reaction that can occur especially in children)
Who should check with a doctor or pharmacist first
- Causes drowsiness; the label warns marked drowsiness may occur and to be careful driving or operating machinery until you know how it affects you.
- Avoid alcohol, sedatives, and tranquilizers, which the label warns may add to drowsiness.
- Do not use with any other product containing diphenhydramine (including some topical anti-itch products), to avoid taking too much.
- Pregnancy or breastfeeding: the label says to ask a health professional before use.
- Children: MedlinePlus advises not giving it to children ages 2 to 5 except on a doctor's advice, and the OTC Benadryl label directs not to use it in children under 6; antihistamine overdose can be dangerous in young children, so check with a pediatrician or pharmacist.
- Older adults: MedlinePlus notes diphenhydramine generally should not be used in adults 65 and older except for serious allergic reactions, and first-generation antihistamines appear on Beers-type geriatric-caution criteria; consult a clinician.
- Ask a doctor before use if you have a breathing problem such as emphysema or chronic bronchitis, glaucoma, or trouble urinating due to an enlarged prostate gland.
- May interact with other sedating drugs, anticholinergics, and certain antidepressants; tell your doctor or pharmacist about all medicines and supplements.
Related situation guides
Frequently asked questions
Is diphenhydramine (Benadryl) the same as Dramamine?+
No, though they are closely related. Dramamine's original formula is dimenhydrinate, a related sedating first-generation antihistamine, while Benadryl is diphenhydramine. In the US, dimenhydrinate is labeled over the counter as an antiemetic for motion sickness, whereas Benadryl's label covers allergy and cold symptoms. Because both are sedating antihistamines, both can cause marked drowsiness.
Does the Benadryl label say it's for motion sickness?+
No. The US OTC Benadryl Drug Facts label lists its uses as relieving hay-fever/upper-respiratory-allergy and common-cold symptoms; motion sickness is not a labeled use. MedlinePlus does list diphenhydramine among medicines used to prevent and treat motion sickness, so it's a use to discuss with a pharmacist rather than one printed on the box.
Does diphenhydramine make you drowsy?+
Yes — it is a first-generation, sedating antihistamine, and its label warns that marked drowsiness may occur. It is not a non-drowsy product, and the label advises caution with driving or operating machinery and avoiding alcohol until you know how it affects you.
Can children take diphenhydramine for motion sickness?+
Be very cautious. MedlinePlus advises not giving diphenhydramine to children ages 2 to 5 except on a doctor's advice, and the OTC Benadryl label directs not to use it in children under 6. Antihistamine overdose can be dangerous in young children, so talk to a pediatrician or pharmacist before giving it to a child.
Is diphenhydramine safe in pregnancy or for adults over 65?+
Those are individual medical decisions. The label directs pregnant or breastfeeding people to ask a health professional before use. MedlinePlus notes diphenhydramine generally should not be used in adults 65 and older except for serious allergic reactions, and first-generation antihistamines appear on geriatric-caution lists. Anyone in these groups should ask a doctor or pharmacist first.
Diphenhydramine or Dramamine for motion sickness — which should I use?+
We don't recommend one over the other; that's a question for your pharmacist. The relevant difference is labeling: in the US, dimenhydrinate (Dramamine) carries an OTC antiemetic indication for motion sickness, while diphenhydramine's (Benadryl's) OTC label is for allergy and cold — even though MedlinePlus lists diphenhydramine as used for motion sickness too. Both are sedating first-generation antihistamines, so both can cause marked drowsiness. Ask a pharmacist which product, if any, fits your situation.
Sources
Related
This page is for general educational and informational purposes only. It is not medical advice and is not a substitute for the advice of a qualified healthcare professional. Dizzout is not a medical provider — we are not doctors or pharmacists. The information here is a general summary drawn from sources such as the FDA-approved label and other public health resources, and it may not reflect the most current changes; the official product label is the authoritative source. Whether any medicine is right for you, and how much to take, are individual decisions that depend on your health, age, and other medicines. We do not provide dosing instructions — always read the product label and follow its directions. Talk to your doctor or pharmacist before starting, stopping, or changing any medication, and never disregard or delay professional medical advice because of something you read here. If you think you may have a medical emergency, contact a doctor or your local emergency number immediately.