A pilonidal sinus, also known as pilonidal cyst, is a small tunnel or hole that forms in the skin, usually at the top of the buttock cleft, just above the sacrum. It can become filled with hair, debris, and other skin particles, leading to infection and the formation of a cyst. Here’s more information about pilonidal sinus:

Causes: The exact cause of pilonidal sinuses is not always clear, but several factors may contribute:

1. Hair Growth: Ingrown hairs or hairs penetrating the skin may play a role.
2. Friction and Pressure: Activities that involve prolonged sitting or friction in the buttock area can contribute.
3. Poor Hygiene: Lack of proper hygiene may lead to the accumulation of debris in the area.
4. Genetic Predisposition: Some individuals may be more prone to developing pilonidal sinuses due to genetic factors.