Sebaceous cysts are small, non-cancerous lumps that form under the skin. They occur when the sebaceous glands, which produce oil to lubricate the skin, become blocked. These cysts are usually filled with a thick, yellowish substance called sebum and can appear anywhere on the body, but are most commonly found on the face, neck, and back. While sebaceous cysts are generally harmless, they can become inflamed or infected, leading to discomfort. Treatment options include draining the cyst or surgical removal, especially if it causes pain or cosmetic concerns. Regular skin care can help prevent their formation.