THE popular blue soap is said to serve a variety of non-laundry purposes, including its use by women in a delicate home treatment that doctors are warning against.

For women who use the soap to regain elasticity after childbirth, age or many sexual partners, it can harm rather than help, gynaecologist Dr Charles Rockhead said.

The use of cake soap has been touted as miraculous by many women who can’t afford surgery or more expensive methods of regaining their pre-childbirth flexibility. And while Dr Rockhead said it does work, at least temporarily, the practice could also cause contact dermatitis (rash or inflammation of the vagina), or leave the vagina vulnerable to infections like yeast.

“About 60 per cent of your body mass is water, so basically what the soap does is that it will dry out the water, forcing the vagina to contract,” Dr Rockhead said. “So in the same way that alum (aluminium hydroxide, which is also used by women worldwide) works, that’s how cake soap works.”

He said as a result of the pulling out of the water from the tissues, there’s automatic shrinkage.

“Remember the vagina is maintained healthy by a particular germ called lactobacillus (good bacteria),” he explained. “It acts on the glycogen germs and converts the area into acidic pH, and because of that acidity it helps to prevent the growth of bad bacteria that normally lives there.”

When the good bacteria is damaged, women are more prone to getting infections.

Another disadvantage, Dr Rockhead said, is that some women may be sensitive to chemicals which can cause a reaction resulting in chemical vaginitis.

“It (using cake soap or alum) is not something that should be practised,” Dr Rockhead warned. “There are non-surgical ways that work such as kegel exercises, and balls that you can insert to try and tighten up instead.”