A sebaceous cyst
is a benign
, harmless growth
under the skin. They feel like little, smooth rocks embedded in the skin. They start small, and grow over time. Sebaceous cysts are usually found on the scalp
, and genitals
. They are formed when sebum
, a medium-thick fluid produced by sebaceous glands
in the skin, gets trapped and contained. This sebum hardens into a small growth.
They are harmless and painless, and can go away on their own. The sebum can sometimes leak, particularly if the cyst is pressed and "milked", producing a nasty, smelly mess. Sometimes, if they hit a certain size, doctors will recommend removing them.
There is a risk of infection with sebacious cysts. When they become infected, the hard growth loosens and breaks up as the infection spreads through it. The cyst will typically grow rapidly at this point, spreading an infection through the surrounding skin if not promptly removed.
The treatment is to make an incision in the skin over the infected cyst, and pull out the infected cyst tissue, replacing it with gauze that has been soaked with antibiotics. The area is covered, with the gauze poking out through the incision, allowing the wound to continue to drain for a day or two. Afterwards, the packed gauze is removed, and the wound is stitched up.
The problem with treating an infected cyst is that since the cyst tissue is so broken up, it can be very difficult to remove it all. Often, a new cyst will form in the same spot, months later. It's best to remove the cyst when it is whole and uninfected, as the whole thing comes out easily.
On a personal note, I had one of these bad boys on my neck, and it got to be about the size of a thumbnail before getting infected. It then got to be almost the size of a golf ball before I could get in to have it removed. Horrible, nasty thing. They were shooting me up with anaesthesia constantly throughout the operation. It was painful. It really really sucked. And having a seeping, infected wound on your neck for the next two days is anything but attractive. My personal recommendation would be to get these things removed as soon as they are noticed.