If you've got oily skin, you've probably heard the word "sebum" thrown around a lot by beauty experts and brands. But what actually is sebum? And why do some people have too much, and others too little? Plus, what is the best way to regulate sebum levels? We hit up expert dermatologists to find out everything you need to know about skin sebum.

WHAT IS SEBUM

“Sebum is an oily substance released by the sebaceous glands of the skin,” explains Dr Ewoma Ukeleghe, cosmetic doctor, founder of SKN Doctor and ambassador for La Roche Posay. Sebum is a complex mixture of fatty acids, waxes, sugars and other natural chemicals and is essential for skin health. “It helps to minimise water loss via the skin, and help to maintain the skin's flora,” continues Dr Ukeleghe.

Plus, sebum plays a key role in the skin’s defense mechanism. “Sebum exists to help protect the surface of the skin reducing the risk of penetration of external elements and helping to retain moisture in the deeper layers,” says Dr Mervyn Patterson, cosmetic dermatologist at Woodford Medical. “A delicate balance exists on the surface of the skin involving all of the constituents in sebum, normal bacteria and the body's own defence mechanisms ensuring a balanced equilibrium.”

WHAT CAUSES AN EXCESS OF SEBUM?

If your skin is very oily, your body may be producing too much sebum, leading to skin conditions like acne and breakouts. The main cause of an overproduction of sebum is hormonal imbalances, including as a result of puberty and pregnancy. “As well as hormones, heat, exercise and genetics play a part,” says Kate Kerr, acclaimed clinical facialist. “It can also be caused by skin that’s dehydrated, and/or skin that’s irritated from incorrect products.”