Sebaceous glands secrete the oily, waxy substance called sebum (Latin, meaning fat or tallow) that is made of triglyceride oils, wax, squalene, and metabolytes of fat-producing cells. In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus classified as holocrine glands. Seborrhoea is the name for the condition of greasy skin caused by excess sebum.
Sebum is odorless, but its bacterial breakdown can produce odors. Sebum is the cause of some people's experiencing "oily" hair, as in hot weather or if not washed for several days. Earwax is partly composed of sebum.
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