A pilar cyst is a type of benign growth which usually forms on the scalp, just below the surface of the skin. These cysts are more common in women than in men, and are more likely to develop in people of middle age or older. Most people with pilar cysts do not experience any pain, tenderness, or other negative effects, and find there is no need to have the cysts removed.

Pilar cysts are small outgrowths which contain keratin, a fibrous protein which is a primary component of skin and hair. These cysts are derived from hair follicles, and form as an outgrowth of a part of the hair follicle called the trichilemma. This part of the follicle is the outer sheath of the root of the hair. The trichilemma may turn into a cyst if large amounts of keratin are deposited in the area within a short space of time. Because pilar cysts develop from hair follicle roots they are more likely to occur in locations where follicle numbers are high; this is why the cysts are typically found on the scalp.

Up to 10% of the population has one or more pilar cysts. Of these 10%, around 70% have more than one cyst. It is not uncommon for someone to have several cysts, but regardless of how many are present, it is very rare for a pilar cyst to cause any negative effects. There have been a small number of cases where a pilar cyst has become malignant, but this is an extremely rare occurrence.

In most cases, pilar cysts are asymptomatic and do not require any treatment. For some people, however, a pilar cyst may rupture or become infected, leading to pain and tenderness in the area. In such cases some form of pilar cyst treatment is necessary.

If one or more pilar cysts becomes infected the most common treatment is with oral antibiotics. In some cases, topical antibiotics may be required. Ruptured or chronically infected cysts may require more permanent treatment, which is carried out in the form of surgical removal.

Removal of pilar cysts is a minor surgical procedure which requires only a local anesthetic. A small incision is generally enough to remove the intact cyst, after which the wound can be closed. Sometimes a sample of the cyst may be taken and tested in a laboratory to ensure it is benign. The rarity of malignant pilar cysts means this is a rare occurrence; in most cases a biopsy is not necessary.