A sebaceous cyst is a tiny sac filled with keratin, the tough protective protein that ordinarily lines the outermost layer of the skin. Basically, a sebaceous cyst occurs when the protein that is supposed to on the skin gets trapped in the skin.
A sebaceous cyst is unlike acne in that acne is an accumulation of oil that is supposed to flow on the skin getting trapped in the skin. A pimple, however, can become a sebaceous cyst if the outer layer of skin, the keratin, falls into a pore and the pore is sealed over by new growth of skin.
Since sebaceous cysts are associated with the sebaceous glands, the specialized tissues in the skin that produce the fatty sebum that keeps the skin lubricated, sebaceous cysts often contain fat. This fat can become rancid so that bursting the cyst releases an extremely unpleasant odor.
Reasons you should have a doctor look at sebaceous cyst
There are reasons you should have a doctor look at any skin growth you suspect might be a sebaceous cyst. If you have multiple cysts, you could have a relatively uncommon condition that causes both cysts on the face and pre-cancerous cysts in the colon. If you have a cyst over your skull, it is possible that the cyst could lead directly to the skull or even the brain, and breaking the cyst could expose you to life-threatening infection. These conditions are quite rare, but they need to be ruled out, and only a doctor can make the diagnosis.
Many people confuse sebaceous cysts with cold sores. A cold sore will develop a crust, while a sebaceous cyst will not. Sebaceous cysts can be found on the face, trunk, arms, nipples, or genitals, but they are most common on the face.
Often these cysts occur in a hair follicle, the hair being too fine to see with the naked eye. There is usually only one sebaceous cyst on the face. Cysts can become cancerous, but this outcome is very rare.
If there's one thing not to do to a sebaceous cyst, it's to try to break it open. Opening a sebaceous cyst exposes tissues beneath the skin to infection. And if your skin has mostly gold or brown skin tones, that is, you are of Asian or African descent, breaking a sebaceous cyst can cause permanent darkening of the skin. Breaking open a sebaceous cyst can cause a colorless bump to be replaced by "bump-less" color.
Opening the cyst surgically
Opening the cyst surgically, however, can be done in way that does not lead to permanent discoloration of the skin. The dermatologist makes a tiny nick in the skin, just 2 to 3 mm (about 1/10 of an inch) long. The doctor then presses hard to make the keratin and fat inside the cyst pop out. Gauze or a splatter shield should be used to protect the physician from spraying of cyst contents. Usually, the dermatologist then puts one or two crystals of iodine inside the cyst so that it will not come back. The iodine itself, however, has to be removed at a second office visit a few weeks later.
This very minor operation to remove a sebaceous cyst usually does not require stitches, but preventing future discoloration of the skin does require applying pressure to the wound for 1-2 hours after the cyst is removed. Come to the dermatologist's office prepared to hold a compress to your face for up to 2 hours after the procedure. Pain from extraction, fortunately, is usually very minor.
There are a few ways that sebaceous cyst removal at the doctor's office can go wrong. Here are the most common complications of the procedure :
- The contents of the cyst literally spray across the room. This, of course, is more of a problem for your doctor and nurse than for you. The doctor and staff may wear glass face shields while performing the procedure.
- The cyst just will not come out through the tiny incision. Generally, your doctor will press on the cyst with both thumbs—this may hurt—to remove the material trapped in the cysts. If this does not work, the incision may have be widened and you may need stitches. This generally happens when there is scar tissue left from acne.
- A blood clot can fill the space that was occupied by the cyst. Keeping pressure applied to the incision after the procedure keeps this from happening.
- The "cyst" turns out not to be a cyst. Sometimes the contents of the follicle are solid, which is a sign that the growth is not a sebaceous cyst. In this case the dermatologist will remove the entire mass and send it off to the lab to be examined for cancer.
Can you take care of a sebaceous cyst without seeing a doctor?
If you have multiple lumps or bumps, you really need to see a doctor to rule out a more serious condition. If you have just one lump or bump, you can try the melt-it-away method.
For self-treatment of a sebaceous cyst, apply a water bottle or a heating pad to the affected skin every day, preferably twice a day, for at least 10 days. It is possible that heat will encourage the fatty sebum to drain from the cyst—but beware, the cyst can break open at a time of its own choosing. You really don't want to be at work or eating lunch with friends when your sebaceous cyst breaks open and squirts its contents across the table. Self-treatment of sebaceous cysts is possible, but most people will get better results from medical care.
Different sources recommend the following home remedies for sebaceous cysts:
tea tree oil has anti-inflammatory and anti-bacterial properties and is effective in treating different conditions 
applying aloe vera gel directly on a sebaceous cyst has pain-relieving and healing properties.
castor oil heals has an anti-inflammatory effect and reduces itching.