The term “sebaceous cyst” refers to a non-cancerous cyst of the skin. There are two types of sebaceous cyst: Epidermal cyst that originates from the upper layer of skin (epidermis), and Pilar cyst that originates from hair follicles. It’s mainly pathologists that worry about these differences. In practice, they both appear very similar – as a firm skin coloured lump.
A Sebaceous cysts forms out of your sebaceous gland. This gland produces the oil, called sebum, that coats your hair and skin. The sebum is the same consistency as toothpaste, yellowish in colour, and doesn’t smell very nice!
Cysts can develop if the gland or its duct becomes damaged or blocked. This generally occurs due to a trauma to the area.
The trauma could be a scratch, a surgical wound, or a skin condition, such as acne. Sebaceous cysts grow slowly, so it could be weeks or months after a trauma before you notice the cyst.
Other causes of a sebaceous cyst may include a deformed duct or an underlying genetic condition such as Gardner Syndrome or Basal Cell nevus syndrome.