Hidradenitis suppurativa (HS) is not caused by poor hygiene, and you can’t catch it from someone else. It’s a chronic inflammatory skin condition that develops when hair follicles in areas like the armpits, groin, and buttocks become blocked, rupture beneath the skin, and trigger a strong immune response. The condition affects roughly 0.1% to 1% of the population, most commonly appearing between ages 18 and 39, and women are diagnosed more than twice as often as men.
There’s no single cause. HS develops from a combination of genetic predisposition, immune system dysfunction, hormonal shifts, and lifestyle factors that interact in ways researchers are still working to fully understand.
What Happens Inside the Skin
HS starts with the hair follicle, not the sweat glands (though the condition was once blamed on them). The process follows a predictable sequence: a hair follicle becomes clogged with skin cells and debris, much like a deep pimple. But instead of resolving on its own, the blocked follicle eventually ruptures beneath the surface of the skin. When that happens, the contents of the follicle spill into the surrounding tissue, and the immune system reacts as if a foreign object has invaded the body.
This triggers intense inflammation. The skin forms painful, deep lumps that can fill with fluid, connect to each other through tunnels under the skin, and recur in the same areas over months or years. Unlike a simple skin infection, the underlying problem is the body’s own inflammatory response spiraling out of control in response to ruptured follicles.
Genetics and Family History
Some people carry gene mutations that make them more susceptible to HS. Researchers have identified mutations in a group of genes responsible for producing a protein complex involved in cell signaling. When these genes don’t function properly, the hair follicle lining doesn’t develop normally, making blockage and rupture more likely.
These mutations have been found in families where multiple members have HS across generations. If one of your parents or siblings has the condition, your own risk is higher. That said, most people with HS don’t have an identifiable single-gene mutation. The genetic picture is more complex, likely involving many small inherited variations that each contribute a little to overall risk.
An Overactive Immune Response
The immune system plays a central role in turning what starts as a clogged follicle into a chronic, recurring condition. In HS lesions, researchers find a striking overabundance of certain inflammatory immune cells. These cells flood the affected skin and release a cascade of chemical signals that promote swelling, redness, pain, and tissue damage.
Specifically, immune cells in HS skin produce high levels of signaling molecules that drive inflammation, including some of the same molecules involved in conditions like psoriasis and Crohn’s disease. The system that normally keeps inflammation in check appears to be overwhelmed, so the inflammatory response doesn’t shut off the way it should. This is why HS is classified as an autoinflammatory condition rather than an infection.
Hormonal Influences
HS typically first appears after puberty, and many women report that their flares follow a pattern tied to their menstrual cycle. Hormonal shifts during pregnancy, breastfeeding, and menopause can also change how active the disease is, though not always in predictable directions. Some women experience improvement during pregnancy while others get worse.
The exact role hormones play isn’t fully mapped out yet. Estrogen and progesterone levels clearly influence disease activity for many patients, but researchers haven’t pinpointed the precise mechanism. The fact that HS is more than twice as common in women as in men, and that it tends to appear during hormonally active years, strongly suggests that sex hormones help set the stage for the condition.
Smoking and Body Weight
Smoking is one of the strongest modifiable risk factors for HS. Studies have found that people with HS are about four times more likely to be smokers than the general population, and smoking rates of 70% to 90% have been observed in HS patient groups. One large study found that continuing to smoke increased the risk of developing HS by about 24%, and people who increased their cigarette consumption had a nearly 29% higher risk compared to nonsmokers. Heavier smoking also correlates with more severe disease.
Obesity is another significant factor. Excess weight creates more skin-on-skin friction in the folds where HS tends to occur, and fat tissue is metabolically active, producing inflammatory signals that may fuel the condition. HS is also linked to metabolic syndrome, a cluster of conditions including high blood sugar, abnormal cholesterol levels, and high blood pressure. It’s not always clear which comes first: chronic inflammation from HS can worsen metabolic health, and metabolic problems can make HS worse, creating a cycle that feeds on itself.
Conditions That Often Occur Alongside HS
People with HS are more likely to have several other health conditions. These include type 2 diabetes, cardiovascular disease, high blood pressure, and abnormal cholesterol. Inflammatory bowel disease, particularly Crohn’s disease, shares some of the same immune pathways and occurs at higher rates in HS patients. Polycystic ovary syndrome (PCOS) is another common overlap, which further supports the hormonal connection.
Joint inflammation, particularly a type affecting the spine and large joints, is also more common. These associations don’t mean HS causes these conditions or vice versa, but they suggest shared underlying biology, primarily chronic, systemic inflammation that affects multiple organ systems.
Why It Takes So Long to Get Diagnosed
One of the most frustrating aspects of HS is how long people go without a correct diagnosis. On average, symptoms begin around age 20, but a formal diagnosis doesn’t come until around age 32. That’s roughly a 12-year gap during which many patients are told they have recurring boils, ingrown hairs, or skin infections. They may be prescribed repeated courses of antibiotics or even undergo unnecessary surgeries on individual lesions without anyone identifying the underlying pattern.
Part of the delay comes from the fact that early HS can look like other common skin problems. Part comes from a lack of awareness among non-specialist doctors. If you develop painful, recurring lumps in your armpits, groin, under the breasts, or on the buttocks, and they keep coming back in the same areas, that recurring pattern is the hallmark that distinguishes HS from ordinary skin infections.
What Doesn’t Cause HS
HS is not caused by being unclean. This is one of the most damaging misconceptions about the condition, and it causes real shame for people living with it. You cannot scrub HS away, and aggressive washing can actually irritate the skin and make flares worse. The condition is also not contagious. You cannot pass it to a partner, family member, or anyone else through physical contact.
HS is a disease of the immune system and the hair follicle, shaped by genetics, hormones, and environmental triggers. People don’t get HS because of something they did wrong. They get it because of a combination of biological factors, most of which are outside their control.