Kao MegRhythm Medical Steam Heat Sheets for Underwear – Unscented, 7 Sheets

The Kao MegRhythm Medical Steam Heat Sheets for Underwear are disposable warming sheets designed to be attached to the inside surface of underwear to provide long-lasting steam warmth around the abdomen or lower back.

This renewed 2026 version is specially designed for use around the lower abdomen and waist, combining a thin, discreet structure with a softer and more breathable skin-contact surface.

Once the individual package is opened, the internal heat-generating material reacts with air and begins warming automatically. No microwave, batteries, hot water or external power source is required.

Each sheet provides approximately 40°C of comfortable steam warmth at the skin surface and continues warming for approximately 5 to 8 hours.

The sustained warmth is designed to reach the abdomen or lower back gradually, helping promote blood circulation and providing a comfortable warming effect during everyday activities.

Designed for the Abdomen and Lower Back

The sheet is specifically shaped for use around the abdomen and waist.

It is attached to the inside surface of fitted underwear, allowing the warming area to remain close to the body without being directly adhered to the skin.

This design makes it suitable for use around the lower abdomen during menstruation, when you want extra warmth around the stomach area, or on the lower back during daily activities.

Attach to Underwear – Not Directly to Skin

Unlike direct-to-skin MegRhythm heat sheets, this version must be attached to underwear.

Peel away the release paper and attach the sheet securely to the inside surface of well-fitting underwear with a sufficiently high rise so that the entire sheet is covered.

The sheet should not be attached directly to the skin.

The inside-facing surface is designed to feel soft against the body while the heating element remains safely separated by the underwear.

Softer and More Breathable Sheet

The renewed 2026 sheet uses a redesigned nonwoven fabric that is approximately 1.4 times softer than the previous version.

The material is also designed to reduce stuffiness during extended wear.

This makes it particularly suitable for use around the abdomen and lower back, where the sheet may remain in place for several hours.

Approx. 40°C for 5–8 Hours

The sheet provides approximately 40°C of comfortable warmth at the skin surface.

The warming effect lasts approximately 5–8 hours, allowing one sheet to provide extended warmth throughout part of the day.

The thin construction helps the sheet remain discreet under clothing without creating excessive bulk.

General Medical Device

This product is classified in Japan as a General Medical Device for thermal therapy.

Its thermal effects include:

• Promoting blood circulation
• Supporting gastrointestinal activity
• Helping relieve pain associated with neuralgia and muscular pain
• Supporting recovery from fatigue

The product is intended for warming therapy around the abdomen and lower back.

Unscented

The sheets are unscented, making them easy to use at work, during commuting, while traveling or around other people without adding fragrance.

Convenient for Menstrual Periods

The sheet can be used during menstruation when additional warmth around the lower abdomen or waist is desired.

Its 7-sheet pack provides one sheet for each day of a full week, making the pack particularly convenient for regular use during the menstrual period.

Air-Activated and Ready to Use

Each sheet is individually sealed.

Once the package is opened, the iron-containing heating material begins reacting with air and gradually warms.

The product should not be heated in a microwave.

No preparation is required before use beyond attaching the sheet correctly to underwear.

Thin and Lightweight

The sheet measures approximately 14.6 × 8.3 cm.

Its thin profile is designed to remain unobtrusive underneath clothing while still providing a broad warming area across the abdomen or lower back.

7 Individually Packed Sheets

Each box contains 7 single-use sheets.

Individual packaging keeps each heat sheet sealed until needed and makes it convenient to carry single sheets in a handbag, travel pouch or workplace drawer.

Each sheet is intended for one-time use only.

Important Use Information

Always attach the sheet to the inside surface of underwear.

Do not apply directly to the skin.

Use well-fitting underwear with enough coverage to hold the entire sheet securely in place.

Avoid delicate fabrics such as silk or lace, as the adhesive may damage the material.

Do not use while sleeping.

Stop use immediately if the sheet feels excessively hot.

Do not use on injured, inflamed or irritated areas.

Do not use together with topical patches, creams or other warming products on the same area.

People receiving medical treatment, people with diabetes or circulation disorders, people with reduced heat sensitivity, people with fever or inflammatory conditions, and pregnant users should consult a physician or pharmacist before use.

Product Features

• Disposable steam heat sheets for underwear
• Designed for the abdomen and lower back
• Attaches to the inside surface of underwear
• Does not attach directly to the skin
• Approx. 40°C comfortable steam warmth
• Approx. 5–8 hours of warmth
• General Medical Device in Japan
• Helps promote blood circulation
• Supports gastrointestinal activity
• Helps relieve neuralgic and muscular pain
• Supports recovery from fatigue
• Approx. 1.4 times softer than the previous version
• Breathable and designed to reduce stuffiness
• Thin and discreet under clothing
• Unscented
• Air-activated
• No microwave required
• No batteries or electricity required
• Suitable for menstrual-period use
• 7 individually packed sheets
• Single-use design
• Made in Japan

Product Specifications

Product Name: MegRhythm Medical Heat Sheet for Underwear
Type: Disposable Steam Heat Sheet
Contents: 7 Sheets
Medical Classification: General Medical Device
Registered Product Name: MegRhythm Steam Heat Sheet b2
Medical Device Notification No.: 13B2X10461000006
Scent: Unscented
Approx. Temperature: 40°C
Warmth Duration: Approx. 5–8 Hours
Sheet Size: Approx. 14.6 × 8.3 cm
Package Size: Approx. W125 × D49 × H137 mm
Skin-Side Nonwoven Material: PET, Polyethylene, Polypropylene
Heat-Generating Material: Contains Iron Powder
Reusable: No
Microwaveable: No
Country of Origin: Japan