Benadryl in Japan: Diphenhydramine Equivalent OTC
Benadryl isn't sold in Japan. But diphenhydramine — its active ingredient — is. Here's where to find it and how to use it safely.
Benadryl isn't sold in Japan. If you've spent any time searching pharmacy shelves here, you already know this. What's less obvious is that the active ingredient — diphenhydramine — is available, just under a completely different name.
The product you're looking for is Restamin Kowa Sugar-Coated Tablets (レスタミンコーワ糖衣錠). It's a Class 2 OTC medicine, available without a prescription at most pharmacies and drugstores in Japan.
Same Ingredient, Different Brand
Diphenhydramine hydrochloride is the active ingredient in both. The per-dose amount is in the same range — Benadryl UltraTab contains 25 mg per tablet (adults take 1–2 tablets per dose, for 25–50 mg), while Restamin Kowa contains 10 mg per tablet (adults take 3 tablets per dose, for 30 mg).
| Benadryl UltraTab (US) | Restamin Kowa (Japan) | |
|---|---|---|
| Active ingredient | Diphenhydramine HCl | Diphenhydramine HCl |
| Per tablet | 25 mg | 10 mg |
| Adult dose | 1–2 tablets (25–50 mg) | 3 tablets (30 mg) |
| How often | Every 4–6 hours | 3 times daily (4+ hr intervals) |
| Minimum age | 6 years | 5 years |
|
Sources: Benadryl UltraTab — FDA DailyMed (setid: ec2070df-8a8a-4cd1-8830-62655433fb3b) Restamin Kowa — Package insert (revised Dec 2025) |
||
What It Treats
- Hives (urticaria)
- Eczema
- Rashes and skin irritation
- Itching (including allergic itching)
- Rhinitis (nasal allergy symptoms)
Dosage
Take with water or lukewarm water. Can be taken with or without food — try to leave at least 4 hours between doses.
| Age | Tablets per dose | Times per day |
|---|---|---|
| Adults (15+) | 3 tablets (30 mg) | 3 times daily |
| 11–14 years | 2 tablets (20 mg) | 3 times daily |
| 5–10 years | 1 tablet (10 mg) | 3 times daily |
| Under 5 | Do not use | |
Children should take under adult supervision.
The dosage table and ingredient information as printed on the box.
Important Warnings
🚗 No driving or machinery
Drowsiness can occur. Do not drive or operate vehicles or machinery after taking this medicine.
🍺 No alcohol
Do not drink alcohol before or after taking this medicine.
💊 No other antihistamines
Do not take with other allergy medicines, cold medicines, cough medicines, nasal allergy tablets, or motion sickness medicines that contain antihistamines.
🤱 Breastfeeding
If breastfeeding, either avoid this medicine or stop breastfeeding while taking it.
📅 Short-term use only
Do not use long-term. Do not exceed the recommended dose.
Who Should NOT Take It
Do not take Restamin Kowa if you are currently taking:
- Other allergy medicines, cold medicines, cough medicines, nasal allergy tablets, or motion sickness medicines
- Any other medicine containing antihistamines
Also do not take if you are:
- Breastfeeding (unless you stop breastfeeding while taking it)
Consult Before Use
Consult a doctor, pharmacist, or registered salesperson before use if you:
- Are under medical treatment.
- Are pregnant or possibly pregnant.
- Have previously had an allergic reaction to any medicine.
- Have difficulty urinating.
- Have been diagnosed with glaucoma.
Side Effects
Stop taking and consult a doctor, pharmacist, or registered salesperson immediately, bringing this package insert with you, if you notice any of the following:
| Area | Symptoms |
|---|---|
| Skin | Rash, redness, itching |
| Digestive | Nausea, vomiting, loss of appetite |
| Urinary | Difficulty urinating |
If dry mouth or drowsiness persists or gets worse, also stop and consult.
If symptoms do not improve after 5–6 days, stop and consult a doctor, pharmacist, or registered salesperson, bringing this package insert with you.
About That Drowsiness
Diphenhydramine is well known for causing drowsiness — it's the same ingredient used in Japan's OTC sleep aid, Drewell (ドリエル). When taking Restamin Kowa for allergy symptoms, expect some sedation. Avoid it before driving, operating machinery, or anything that needs concentration.
If you're specifically looking for a sleep aid, Drewell is the product — same active ingredient, but marketed and dosed for difficulty falling asleep.
Where to Buy
Restamin Kowa tablets are available at most major Japanese pharmacy chains — Matsumoto Kiyoshi, Welcia, Sun Drug, and others. Look for the red and white packaging with the name レスタミン on the label. It's usually in the allergy or antihistamine section.
You can also order it on Amazon Japan.
Looking for more allergy options?
Browse OTC antihistamines and allergy medicines available in Japan — all explained in English.
Browse allergy medicines →