A skin cyst is a common, non-cancerous growth that forms as a closed sac under the skin. These sacs are typically filled with fluid, pus, or other semi-solid material. They can appear almost anywhere, are generally harmless, and often do not require medical intervention unless problematic.
General Appearance of a Skin Cyst
A typical skin cyst often presents as a round or dome-shaped lump just beneath the skin’s surface. Its size can vary considerably, ranging from a small pea-sized bump to several centimeters across. The color is usually similar to the surrounding skin, though it may sometimes appear slightly yellowish or whitish. If inflamed or infected, the overlying skin can turn pink or red.
When touched, a skin cyst generally feels smooth, firm, and is often movable under the skin. Many common types, such as epidermoid cysts, may feature a small, dark dot or “punctum” in the center. Occasionally, a cyst might rupture or become irritated, discharging thick, cheesy, and sometimes foul-smelling material, primarily keratin and cellular debris. Cysts are frequently found on the face, neck, trunk, and scalp.
Differentiating Cysts from Other Bumps
Distinguishing a skin cyst from other common bumps involves specific visual and tactile characteristics. Pimples, for instance, are typically smaller, redder, and often inflamed, usually resolving more quickly than cysts. Severe forms of acne, known as cystic acne, can present as larger, pus-filled lesions but are distinguished by their inflammatory nature and association with clogged pores.
Boils, also called furuncles, are usually more painful, red, and swollen, often featuring a central pus-filled head. They develop around hair follicles and signal an active bacterial infection, whereas an uncomplicated cyst is generally painless. Lipomas are fatty growths, typically softer, doughy to the touch, and feel more movable or “slippery” beneath the skin than a cyst. Moles and skin tags, in contrast, are usually pigmented growths either flat on the skin or protruding from the surface, lacking the fluid-filled sac structure characteristic of a cyst.
When to Consult a Professional
While most skin cysts are benign, certain signs indicate that medical evaluation is appropriate. Consult a healthcare professional if a cyst shows signs of infection, such as increasing redness, warmth, tenderness, swelling, or pus drainage. Rapid growth or a noticeable change in appearance also warrants medical attention.
Seek advice if the cyst becomes painful, particularly if the discomfort interferes with daily activities. A consultation is also recommended if the cyst is in a sensitive area, causes cosmetic concern, or if its nature is uncertain. If a previously treated cyst reappears, a professional should check it.