Hidradenitis suppurativa (HS) is an inflammatory skin condition that causes painful bumps and boils to develop underneath the skin and between the skin folds. This condition is sometimes called acne inversa, though these bumps aren’t related to acne, even though they may look and feel like pimples.
While the exact cause of HS is currently unknown, being assigned female at birth, smoking, and having certain underlying health conditions can increase your risk of developing HS.
Researchers know that hidradenitis suppurativa occurs when the skin’s hair follicles become blocked or clogged. However, they don’t know why this clogging happens. If your hair follicles are blocked, you have a higher risk of developing HS, which may lead to an inflammatory response, causing symptoms like swelling, pain, sores, and pus-filled bumps.
What blocks the hair follicle in the first place? Researchers have found that it’s a combination of things normally found in the skin, like keratin (a protein), sweat, and bacteria.
As keratin, sweat, and bacteria build up and become trapped in your hair follicles, a bump or abscess (a bump filled with pus) can form. Sometimes, this build-up also leaks out of the follicle and blocks nearby follicles, causing multiple lumps and abscesses to develop in one area of the body.
Even though the keratin, sweat, and bacteria your skin produces can lead to these bumps, most people with HS don’t have health conditions that affect their sweat glands or keratin production. It appears that people with HS have a heightened immune system response to blocked follicles, which can trigger the inflammatory process that causes HS.
Research shows that hidradenitis suppurativa tends to run in families. About 30-40% of people with HS have a first-degree relative (e.g., a parent or sibling) with the condition. Experts believe that HS may have an autosomal dominant pattern of inheritance in some families, which means you can inherit the condition from only one parent with a genetic mutation associated with HS.
Studies estimate that people with HS have a 50% chance of passing on this genetic mutation to their children. While more research is ongoing, experts have found that the genes that can play a role in the development of HS include NCSTN, PSEN1, or PSENEN.
However, just because you inherit an affected gene doesn’t guarantee you’ll develop HS. Some people with HS also don’t have a family history of the disease. That’s because most people who live with HS have experienced a combination of genetic and environmental triggers that have led to their condition.
While anyone can develop hidradenitis suppurativa, researchers suspect some people are more likely to develop the condition than others. Consider the following factors:
- Age: Many people with HS begin noticing symptoms during puberty, but it can appear anytime before age 40. The most common age range for developing HS is 21-29 years old.
- Sex: HS is three times more common in people assigned female at birth than in their male counterparts. Experts believe that fluctuating hormone levels in women (such as during periods, pregnancy, and menopause) can increase the risk of developing HS. Studies also show that women who already live with HS tend to experience symptom flares (periods where symptoms are most active) when hormone levels change.
- Race and ethnicity: Black people are more likely to get HS than other ethnicities. Black and biracial women, in particular, have a higher risk of developing the condition than other people living in the U.S.
It’s also important to know that misdiagnosis of HS is common, so more inclusive research and better statistics are still needed to understand how many people experience the condition and what other factors can increase your risk of experiencing HS symptoms.
For most people who have a hidradenitis suppurativa diagnosis, more than one factor occurring at the same time caused their condition. For example, this may include inheriting an HS gene and entering puberty as an adolescent female.
While family history, age, sex, and ethnicity all play a role in determining who gets HS, there are also individual risk factors that can further increase the likelihood of developing the condition, especially if you are part of another HS risk category. Common risk factors include:
- Smoking tobacco: Smoking is perhaps the most common environmental risk factor for HS. As many as 70-90% of people with HS report having a history of smoking or using tobacco products. Research believes that smoking frequently can affect sweat gland production, increasing the risk of clogged hair follicles.
- Obesity: Studies show that people with HS often experience more severe symptoms if they also live with obesity. Obesity can trigger other potential risk factors of HS, like increased hormonal changes, skin-to-skin friction, and increased sweat and keratin production.
- Other follicle disorders: Some conditions related to blocked or clogged hair follicles, like severe forms of acne, pilonidal sinus, and scalp diseases that cause scarring and hair loss, have all been associated with an increased risk of HS.
- Inflammatory bowel disease (IBD): Having IBD doesn’t necessarily increase your risk for HS, but there is a strong association between the two conditions. Research shows that many people live with both HS and Crohn’s disease (a type of IBD) at the same time. This may be because smoking is a primary risk factor for both diseases.
- Psoriasis: This skin condition is associated with a higher risk of HS. In current studies, most people with both conditions developed psoriasis first and then HS—and some even developed HS as a result of psoriasis treatment. More research is still needed to understand why psoriasis and HS are connected. However, shared risk factors (like smoking and obesity) or immune system inflammation might increase the risk of both conditions.
Hidradenitis suppurativa (HS) is a painful and chronic inflammatory skin condition that causes bumps and abscesses to form under the skin. HS typically occurs because of blocked hair follicles, but why your hair follicles become clogged is still a research mystery.
Researchers have identified that certain factors, such as having a family history of HS, being assigned female at birth, and smoking tobacco, can all increase your risk of developing this condition.