The human body occasionally creates structures and substances which serve no discernible purpose. Such is the case with a membrane-covered growth called a cyst. A cyst is generally formed on the surface of an organ or in the empty spaces between muscle and skin tissues. Generally speaking, most cysts are harmless (benign) and self-contained, filled with air, infected fluids or semi-solid substances such as sebum.

A cyst may be caused by a defect during fetal development, an infection or some unknown reason. Many people may notice small, hard lumps under their forearms or wrists, for example. These lumps are actually a form of cyst called a sebaceous cyst. A lump in the wrist may be a ganglion cyst. Some people develop a cyst on their vocal cords. It is not unusual to discover a cyst under one's scalp or face.

While a cyst may not be harmful or cancerous, it can be extremely painful. Soldiers who frequently spent time riding in jeeps during World War II sometimes reported a painful 'blister' near their tailbones. Doctors soon determined the real cause of the pain was a cyst formed by ingrown hairs near the coccyx. Based on the Greek words for 'hairy nest', the condition is now known as a pilonital cyst. Those who have a sedentary lifestyle, suffer from obesity or have substantial lower back hair are especially susceptible to pilonital cyst development. Surgical intervention may be necessary if the cyst does not drain naturally.

The condition known as cystic fibrosis is aggravated by numerous cysts forming and subsequently bursting in the lung cavity. The mucus release from each cyst drains into the lungs, creating a life-threatening shortness of breath if not kept in check. A cyst on the ovary is usually not malignant, but it can continue to grow into a large mass and cause painful crowding of abdominal organs.

Many times a suspicious cyst is examined through a procedure called needle aspiration. The fluids and other materials drawn from the cyst are tested for infection and any evidence of uncontrolled cell growth. Many times a physician will prescribe antibiotics and pain relievers instead of recommending surgical intervention. A sebaceous cyst may cause an unsightly lump under the skin, but removal is not medically necessary. More severe cyst formations may require lancing, followed by a regime of sterile bandages and antibiotics. Until a severe cyst has drained completely, secondary infections are always a concern.