Legend says that Egyptian queen Cleopatra bathed daily in sour donkey's milk to improve the complexion of her skin and reduce wrinkles.

传说埃及艳后每日用酸驴奶沐浴，以改善肤色、减少皱纹。

Dr Altcheck doesn't recommend bathing in rotted milk, but says the dairy product does contain protein and skin-nourishing minerals like vitamin E and zinc.

Vitamin E neutralizes the effect of free radicals, which are molecules that cause skin dryness, fine lines and wrinkles. They also damage collagen, or the connective tissues that keep your skin together.

Meanwhile, Vitamin D has been shown to minimize acne, increase skin elasticity, and lessen the appearance of dark spots.

Dr Altcheck also says that the two vitamins have healing properties.

'Vitamin D and vitamin E will also help accelerate how fast the skin repairs itself from UV rays, wind, sun, contaminants and pollution,' he told Daily Mail Online.

The dermatologist adds that another key ingredient in milk, lactic acid, also has skincare benefits.

'Lactic acid is a healing product which helps the skin become smoother,' he said.

Lactic acid is an alpha hydroxy acid, which encourages the skin to shed its old, dead skin cells to reveal the new, healthy skin cells hidden underneath.

In higher concentrations, it also works to reduce pigmentation and brighten the skin.