Hidradenitis suppurativa (HS) develops when hair follicles in areas like the armpits, groin, and under the breasts become blocked and eventually rupture beneath the skin, triggering a powerful inflammatory response. It is not caused by poor hygiene, and it is not contagious. The condition affects roughly 0.4% of the U.S. population, with women diagnosed about four times more often than men.
HS is the result of several overlapping factors, primarily genetics, immune system dysfunction, and hormonal influences, often made worse by environmental triggers like friction, smoking, and excess weight. Understanding what drives the condition can help you recognize early signs and reduce flares.
It Starts in the Hair Follicle
The primary defect in HS is in the hair follicle itself. A follicle becomes plugged with skin cells and debris, much like what happens with a pimple, but the process goes deeper. Instead of draining to the surface, the blocked follicle eventually ruptures underneath the skin. When that happens, the contents spill into surrounding tissue, and the immune system treats it like a foreign invader.
This triggers an intense inflammatory reaction that produces the painful lumps, abscesses, and tunnels beneath the skin that characterize HS. Over time, repeated cycles of blockage, rupture, and inflammation can lead to scarring and permanent tunnel-like tracts connecting lesions under the skin. The process tends to recur in the same areas because those regions have a high concentration of hair follicles and skin folds.
Genetics Play a Major Role
Between 30% and 56% of people with HS report a family history of the condition, and the percentage is even higher among those whose symptoms started at a young age. Twin studies from the Netherlands and Denmark found that genetics account for 77% to 80% of the risk for developing HS, making it one of the more heritable skin conditions.
In a small number of families (fewer than 7% of cases), HS follows a single-gene inheritance pattern. These rare cases involve mutations in genes that control a signaling pathway important for normal hair follicle development. Researchers have identified more than 59 different mutations across three specific gene components in affected families. But for most people with HS, the genetic picture is more complex, likely involving multiple genes that each contribute a small amount of risk.
The Immune System Overreacts
HS is fundamentally an inflammatory disease. When a follicle ruptures, the immune response that follows is far more aggressive than what you’d see with an ordinary blocked pore. Studies comparing HS skin to healthy skin have found dramatically elevated levels of key inflammatory signaling molecules. The most prominent of these drive the kind of sustained, tissue-damaging inflammation that leads to scarring.
About 80% of certain immune cells in HS lesions actively produce these inflammatory signals, compared to roughly 50% in healthy skin. This isn’t a simple infection. It’s the body’s own immune system attacking tissue in a way that perpetuates the cycle of damage. That’s why antibiotics alone rarely control HS and why treatments targeting the immune system directly are often more effective for moderate to severe cases.
Smoking Increases Your Risk
Smoking is one of the strongest modifiable risk factors for HS. People who continue to smoke have a roughly 24% higher risk of developing the condition compared to nonsmokers. Those who increase the number of cigarettes they smoke over time face an even steeper risk, about 29% higher than nonsmokers.
Nicotine and other chemicals in tobacco smoke are thought to promote follicular plugging and amplify inflammation in the skin. Quitting doesn’t guarantee HS will resolve, but it removes a significant contributor to flares and disease progression.
Hormones and Who Gets HS
HS typically appears after puberty, and the average age at diagnosis is in the early 40s, though many people experience symptoms years before getting a formal diagnosis. The strong female predominance (a 4:1 ratio over men) points to a hormonal component. Many women with HS notice that flares worsen around their menstrual cycle, suggesting that fluctuations in estrogen and progesterone play a role in disease activity.
The exact hormonal mechanism is still not fully understood. Researchers know that hormone levels influence the condition, but the specific pathways remain an active area of investigation. What’s clear is that life stages involving hormonal shifts, such as puberty, menstruation, pregnancy, and menopause, can all affect HS severity.
Friction, Heat, and Sweat Make It Worse
While external factors don’t cause HS on their own, they can trigger flares in someone who already has the condition. Tight clothing that presses against the skin, traps moisture, or creates friction in skin folds is a common culprit. Heat and sweat promote the growth of bacteria and other microbes on the skin surface, adding to irritation and inflammation.
One bacterium in particular is found in higher than normal amounts on HS skin and may worsen local inflammation by activating certain immune cells. This doesn’t mean HS is an infection, but it does mean that keeping affected areas cool, dry, and free from excessive friction can help reduce flare frequency. Loose, breathable fabrics and moisture-wicking materials are practical choices.
Diet May Influence Flares
Several dietary factors have been linked to HS flares, though the evidence is still evolving. In one small study, 12 patients who eliminated brewer’s yeast from their diet (cutting out bread, vinegar, soy sauce, beer, wine, and fermented cheese) had no flares over a full year. The flares returned once they resumed their usual diet.
Some people with HS also report that dairy, alcohol, or gluten trigger their symptoms, though dairy elimination alone hasn’t consistently reduced flares in studies. A Mediterranean-style diet, heavy on fresh vegetables, fruits, whole grains, fish, and olive oil while avoiding processed foods, has been associated with fewer flares in survey data. If you suspect a food sensitivity is contributing to your symptoms, a structured elimination diet with a healthcare provider can help identify your personal triggers.
What HS Is Not
One of the most damaging misconceptions about HS is that it results from being unclean. The British Association of Dermatologists states plainly: poor hygiene does not cause HS. The condition is also not contagious and cannot be passed to another person through any form of contact. These myths contribute to the shame and isolation many people with HS experience, and they delay diagnosis by an average of seven to ten years in many cases.
HS is a chronic inflammatory condition rooted in genetics and immune dysfunction. Recognizing it as such is the first step toward effective management and reducing the stigma that surrounds it.