Most of the parasites that affect humans undergo the cystic stage. In this stage, they get covered by a protective wall and prepare for a full fledged infection. Such infections can also give rise to cysts on the surface or within the human body. The hydatid disease is an example and it affects both humans and animals. The only way of battling and getting cured of these cysts is to battle the parasite.

A cleft cyst which is also called a cleft sinus is often the result of a birth defect. just like the gill slits of fishes, a lesion is formed on one or either sides of the neck and it begins to collect drainage fluid from the sinuses. Though the cyst is formed in the embryonic stage, it cannot be detected till adulthood. The fluid accumulation in the cleft cyst makes it prone to secondary infections. It can become inflamed and result in an upper respiratory tract infection or an abscess. Then, it leads to difficulty in swallowing and even in breathing.

An inflammation is actually an immune response to an injury, an infection or an irritation. Immune cells move to the affected site through the blood stream. The blood vessels at the site become permeable, the temperature rises and phagocytes and other cells fight the infection and irritation. Sometimes, the immune system faces a hang up where these immune cells begin to combat the body cells. These are called chronic inflammations and they often result in the growth of cysts.

The human body has innumerable ducts and openings for sweat, saliva, sebum and other secretions. When these ducts get blocked, plugged or clogged, the secretions collect and cause a local swelling. In course of time, this becomes a benign growth or cyst. At times these swellings are confused for teratomas or neoplasms which imply proliferation of cells. The cysts that are caused this way only need the blockage to be cleared and they slowly disappear. Such benign tumors can also appear on the breasts. They are not cancerous and one need not deal with them unless they cause pain and discomfort. Then, surgery is the most preferred option.

Cystic fibrosis is is a recessive genetic disorder that affects the lungs, pancreas, intestine and liver. Cysts get formed within all the above mentioned organs and cause difficulties in breathing, digestion and reproduction. The gene that codes for the protein CFTR ( cystic fibrosis transmembrane conductance regulator) is vital for the regulation of sweat, mucus and the digestive juices. This gene undergoes mutation and causes cystic fibrosis. The CFTR gene usually exists as two working copies. In cases when neither gene works well, cystic fibrosis is the result. The cysts cause grave dangers to the life of the patient and lung transplantation often becomes necessary for survival.

The meniscus is a crescent-shaped fibrocartilaginous structure that partly divides the joint cavity at the knee. A cyst can form as a well-defined lesion along the peripheral margins of the meniscus. The cause for such cysts is believed to be the extruding of the synovial fluid through a horizontal tear in the meniscus. And this tear, in turn, is caused by either hemorrhage, trauma or degeneration of the mucus in the region. These cysts are known to happen mostly in males in the age range 20-40 and they arise more commonly along the lateral joint margins.

Skin trauma often results in injuries to the hair follicles. When these hair follicles swell in response, the result if often a cyst. Such cysts are known as sebaceous cysts which arise as small bumps or lumps under the skin. They contain the protein keratin which appears as a ‘cheesy’ or ‘paste-like’ extrusion with a foul odor. These can occur on any part of the body but are most often seen to appear on the neck, face, trunk and the genitalia. These small lumps move freely under the skin and occasionally cause an infection too.