A You probably don't have a sebaceous cyst - it's more likely to be an epidermoid cyst, as it's on your face. The other common variety is the pilar cyst, which tends to appear on the scalp. It also runs strongly in families, and a child of a parent who suffers from pilar cysts has a 50 per cent greater chance of developing them himself.
These cysts are enclosed sacs with a lining. They are filled with keratin, the material used in hair and which make up the skin's outermost layer, in either a liquid or semi-solid state. They become red and sore when infected, and can discharge a cheesy, foul-smelling pus. In size, they can range from smaller than a pea to as large as several centimetres across.
Medicine is limited in its responses to cysts and, ultimately, will suggest minor surgery to remove it altogether if the cyst is visible and unsightly.
Cyst removal is the most common minor surgical procedure in the West, but it is still not without problems. Scarring is a very real issue, and much depends on the skin type. Plenty of people will go on to develop large scars known as 'keloids', which can look worse than the cyst itself. It's also not unusual for the cyst to grow again, requiring further surgery.
Doctors also prescribe antibiotics to reduce infection, or even steroids, which are very powerful, but come with a dubious safety track record. And, of course, they don't really clear up the cyst for good.
There are two ways to treat a cyst: either expelling it, or reabsorbing it, which might be the better option if, as in your case, the cyst has a root and is continually filling up again.