A sebaceous cyst, more accurately called an epidermoid cyst, is a noncancerous fluid-filled lump under the skin that forms due to a blockage of sebaceous glands or oil glands. These glands produce sebum, an oily substance that lubricates the skin, but the cyst itself is usually filled with keratin, a protein, rather than sebum. Sebaceous cysts appear as small, round, painless bumps beneath the skin on areas like the face, neck, back, or genitals. They grow slowly and can vary in size. Sebaceous cysts are typically harmless but can become painful or inflamed if infected. They may sometimes leak a white or yellowish oily substance. Treatment often involves surgical removal to prevent recurrence, especially if the cyst becomes large, painful, or infected. Antibiotics may be used if the cyst is infected, but they do not remove the cyst itself. Complete surgical excision usually prevents the cyst from coming back, though new cysts can develop in predisposed individuals. In summary, sebaceous cysts are benign, slow-growing cysts under the skin caused by blocked oil glands, mostly filled with keratin, and can be treated effectively through simple surgical excision if problematic.
