Sebum is an oily substance produced by the sebaceous glands, which are microscopic glands found in the middle layers of the skin, near hair follicles. Sebum is a complex mixture of lipids, including glycerides, free fatty acids, wax esters, squalene, cholesterol esters, and cholesterol. Sebum has several functions, including:

• Moisturizing: Sebum helps keep the skin hydrated and flexible by reducing water loss from the skin surface.

• Protection: Sebum forms a protective coating on the skins surface, which helps protect it from harmful pathogens, such as bacteria and fungi.

• Lubrication: Sebum lubricates the hair to prevent it from drying out.

However, an overproduction of sebum can lead to oily skin, which can cause problems such as clogged pores, blackheads, and pimples. Excess sebum combined with dead skin cells can form a plug inside the pore, which results in blackheads and pimples. This plug also traps excess bacteria in the pore, which can lead to inflammation and breakouts.

In summary, sebum is an oily substance that helps moisturize and protect the skin, lubricate the hair, and repel certain bacteria. However, an overproduction of sebum can lead to oily skin and various skin problems.