How does diphenhydramine work?
Diphenhydramine blocks histamine receptors, reducing allergy symptoms like itching, swelling, and sneezing. It also has a sedative effect, which can help with sleep problems and motion sickness.
What is diphenhydramine used to treat?
Diphenhydramine is commonly used for:
- Allergic reactions (such as hay fever, hives, or insect bites)
- Colds and flu symptoms (to relieve runny nose and sneezing)
- Motion sickness
- Short-term sleep problems (insomnia)
- Mild anxiety (off-label use in some cases)
Who can take diphenhydramine?
Diphenhydramine is suitable for most adults and children over 6 years old.
Who might not be able to take diphenhydramine?
Diphenhydramine may not be suitable if you:
- Have glaucoma
- Have severe breathing problems, such as COPD or asthma
- Have difficulty urinating due to an enlarged prostate
- Are taking other sedating medications
Can I take diphenhydramine if I’m pregnant or breastfeeding?
Diphenhydramine isn’t usually recommended during pregnancy or breastfeeding unless advised by a doctor.
What if I miss a dose?
If you forget a dose (for allergy or cold treatment), take it as soon as you remember. If it’s close to your next dose, skip the missed one—do not take two doses at once.
How effective is diphenhydramine?
Diphenhydramine is highly effective at reducing allergy symptoms and promoting sleep, usually working within 30 to 60 minutes.
What should I do if I take too much?
Taking too much diphenhydramine can be dangerous and may cause:
- Extreme drowsiness
- Fast or irregular heartbeat
- Confusion or hallucinations
- Seizures
If you think you’ve taken too much, seek emergency medical help immediately.
What dose of diphenhydramine is usually taken?
- For allergies and colds: 25mg to 50mg every 4 to 6 hours, up to 300mg daily
- For sleep problems: 50mg before bedtime
- For motion sickness: 25mg to 50mg taken 30 minutes before travel, then every 4 to 6 hours as needed
Your doctor or pharmacist will determine the correct dose based on your condition.
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What are the side effects of diphenhydramine?
Common side effects include:
- Drowsiness or dizziness
- Dry mouth
- Blurred vision
- Constipation or difficulty urinating
Serious side effects, such as severe confusion, breathing difficulties, or hallucinations, require urgent medical attention.
How should I take diphenhydramine?
Diphenhydramine is available as tablets, liquid, capsules, and topical creams. Follow the instructions carefully and avoid alcohol, as it can increase drowsiness.
When should diphenhydramine be taken?
- For allergies or colds: Take as needed, following the recommended dose.
- For sleep problems: Take 30 minutes before bedtime.
- For motion sickness: Take before travelling and as needed.
What are the brand names for diphenhydramine?
Diphenhydramine is available as a generic medicine, but some branded versions include:
- Benadryl Night (for allergies and sleep aid)
- Nytol Original (for sleep problems)
- Nytol One-A-Night
- Allerdryl
Final thoughts
Diphenhydramine is an effective antihistamine for allergies, colds, and sleep problems, but it can cause drowsiness. To get the best results, take it as prescribed and avoid alcohol. If symptoms persist or side effects occur, speak to your doctor or pharmacist.
