Legend says that Egyptian queen Cleopatra bathed daily in sour donkey's milk to improve the complexion of her skin and reduce wrinkles.
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.
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.
HOW TO DRAW YOUR BATH
Dr Altcheck says that it's better to use warm milk because it will penetrate the skin faster than cold milk - but warns against staying in the bath for too long.
'It's a double-edged sword because on one hand you want to stay in there long enough to absorb the nutrients,' he said. 'On the other hand, you will become dehydrated if you stay in too long and the water will literally roll out your skin. I would say anything beyond 15 minutes would be harmful.'