Pilonidal cysts are a common skin condition that can cause discomfort. While often asymptomatic, these cysts, typically found in the crease of the buttocks, can develop a strong, unpleasant smell when infected. This article explores what pilonidal cysts are and the specific reasons behind their potent odor when infection occurs.
What a Pilonidal Cyst Is
A pilonidal cyst is a sac-like pocket of tissue that forms under the skin, most commonly near the tailbone in the crease of the buttocks. The term “pilonidal” means “nest of hair,” reflecting that these cysts often contain hair. This condition arises when loose hairs, skin cells, and other debris become trapped beneath the skin surface. The body’s immune system responds to this foreign material, forming a cyst around it that can fill with fluid.
The Bacterial Connection to Odor
The foul smell associated with an infected pilonidal cyst is primarily due to the presence and activity of bacteria. Anaerobic bacteria, which thrive in environments with limited or no oxygen, are particularly prevalent. These microorganisms break down organic matter within the cyst, producing various malodorous compounds as byproducts.
These byproducts include volatile fatty acids and sulfur compounds, such as hydrogen sulfide, known for its rotten-egg smell. Specific anaerobic bacteria often identified include Bacteroides species and anaerobic cocci. Other bacteria like Escherichia coli and Proteus species can also contribute to the complex and offensive odor profile.
Substances Trapped Within the Cyst
The materials accumulating inside a pilonidal cyst provide the fuel for bacterial growth and subsequent odor production. The cyst creates a confined space where various organic substances become trapped. These often include loose hair, dead skin cells, and natural oils from the skin.
When infected, the cyst can also fill with pus, a thick, yellowish fluid. Pus is a mixture of dead white blood cells, bacteria, and tissue debris, all contributing to the overall organic load within the cyst. The breakdown of these diverse materials by bacteria creates a rich environment for the release of pungent compounds.
Why the Smell is So Potent
The potency of the odor from an infected pilonidal cyst stems from a combination of factors related to its environment. The location of these cysts, typically in the intergluteal cleft, creates a warm, moist, and enclosed space. This environment is ideal for the proliferation of anaerobic bacteria, which produce more potent odors compared to bacteria that thrive in oxygen-rich conditions.
The lack of oxygen within the cyst promotes anaerobic decomposition, a process known to generate highly offensive gases. The confined nature of the cyst also means these pungent byproducts become concentrated within the cavity. When the cyst drains, this accumulated, highly concentrated, and foul-smelling material is released.