Skin cysts are common and can occur in both children and adults. They can also be congenital. Cysts can vary in size, from millimetres to several centimetres, and are often filled with tissue fluid, pus, or sebum. Initially, a cyst is not an infection, but it can become infected and develop into an abscess.
Skin cysts usually develop on their own. Most people notice the cyst when it reaches a certain size. They can feel firm or soft and may be slightly tender, especially if they are located in areas exposed to pressure and friction. Sometimes there can be leakage of pus or other fluid, and a small duct can be seen. The content of a cyst can sometimes have an odour. Occasionally, calcium can accumulate in cysts, making them hard. Skin cysts are usually located slightly deeper in the skin, so the surface of the skin is usually unchanged but may appear slightly stretched and red.
There are several types of cysts:
Epidermoid cysts, also known as sebaceous cysts, are common cysts that originate from hair follicles and gradually fill up with newly formed epidermal cells (keratin) and fatty substances. They can often be found on the head, neck, and back.
Dermoid cysts can resemble epidermoid cysts but arise from deeper layers of the skin (dermis) and can contain hair follicles, sebaceous glands, and occasionally even teeth.
Pilonidal cyst, also known as a pilonidal sinus, is sometimes considered a cyst and typically occurs in the lower back. It is more common in young men. The cause can be the accumulation of excess dead skin and sebum in the hair follicles, leading to an infection.
Mucocele is a cyst that occurs in the mouth or on the inside of the lip and is caused bya blocked salivary gland.
Digital myxoid pseudocyst, also known as a finger cyst, occurs at the fingertips or toes. It contains a clear gelatinous fluid that resembles synovial fluid, making the cyst an outpouching of the joint capsule around the finger joint.
Milia can be considered a type of cyst and appear as small yellow-white bumps in the skin, resulting from the accumulation of dead skin cells. The cause is unknown but can be associated with skin damage or eczema, such as atopic eczema around the eyes. Milia can resemble acne. Cysts can also develop from large pimples and are often red, inflamed, and filled with pus.
The treatment of cysts depends on the cause and size and usually involves surgical intervention. Larger cysts may need to be punctured, and the liquid contents can be drained. However, it is often better to remove the entire cyst with its wall to reduce the risk of recurrence. Small cysts can sometimes be punctured using high heat (diathermy) or a fine needle, followed by emptying the contents, which can be effective for milia.
Many types of tumours or lumps under the skin can resemble cysts. Enlarged lymph nodes or hematomas are examples of this. If a lump under the skin continues to grow, it should be examined.
