After Japanese women reported side effects of breast enlargement surgeries with fillers, the Ministry of Food and Drug Safety on Tuesday sent a warning letter to local doctors not to use unauthorized fillers.

The warning went to the Korean Hospital Association, the Korean Medical Association, and the Korean Society of Plastic and Reconstructive Surgeons.

In Japan, patients who underwent breast augmentation operations with fillers reported problems such as lumps, infections, and skin deformity. Japan Society of Aesthetic Plastic Surgery established a guideline to prohibit the use of fillers in breast implants and demanded Japan’s Ministry of Health, Labor and Welfare give license for use.

Fillers are injections made of harmless substances such as hyaluronic acid and calcium phosphate. When injected into the dermal layer of the skin, they improve wrinkles and facial lines. Fillers are usually injected into the forehead, the bridge of the nose, nasolabial folds, lips, and neck.

Some products also received indications for wrinkles on the back of the hand and penis enlargement.

An increasing number of people are using fillers in body parts other than the face. However, no domestic filler has obtained an indication for breast enlargement.

The filler injection is a simple procedure, but a wrong injection into blood vessels could lead to necrosis or blindness.

“The government has not approved fillers for plastic surgeries to be used for breast enlargement. Doctors are advised to notify patients that side effects may occur if fillers are used for breast enlargement other than for authorized use,” the ministry said in the letter.