What is HS? Information about Hidradenitis Suppurativa (HS).

Section One.
What is HS? (in a nutshell)

If you are reading this, there’s a reasonable chance that you’ve found this page because you’re confused about what is happening with your body and you feel you are not getting any answers from the healthcare professionals you meet. You might be tired of being told that what you have is “just boils” or “bad acne.” We are aware that this is an all too common outcome for people living life with HS in the UK & Ireland.

Do not despair. This page is designed to give you the lowdown, and if you want it, the deepest dive on the internet into all the current, evidence based information available about HS. The first step in being able to advocate for yourself is gaining a detailed understanding of HS. Not to tease, but before we try to answer “What HS is”, it may be equally important to state what HS is not, as some stigmas exist.

HS, is not contagious. You cannot catch it from someone else, and it does not spread through touch, shared towels, or being close to someone who has it.

HS is also not a sexually transmitted infection. That matters, because people sometimes assume anything affecting the groin must be linked to sex. HS is a skin condition, not an STI. 

It is not caused by poor hygiene. That idea is common, but it does not fit what current research shows. A better way to think about HS is as a problem with the skin’s own inflammatory systems, rather than a “dirty skin” problem. 

HS is a chronic, recurrent inflammatory disease that affects the body’s immune system. Unlike a simple skin infection, it is a complex condition that can form deep, painful lumps, nodules, and abscesses in skin-fold areas—most commonly the armpits, groin, buttocks, inner thighs, and under the breasts, although HS can occur anywhere on the body.

For many, these aren’t just one-off flare-ups. Over time, these recurring episodes can form persistent, draining tunnels under the skin known as sinus tracts. HS is categorised into three stages using something known as The Hurley Staging System, see below for more on that. Because awareness remains dangerously low, most people spend years navigating this pain in complete silence, feeling like they are the only ones dealing with a body that seems to be turning against them. We hope this page helps you regain some control of the situation.

Recognising the Signs

HS often manifests in ways that are easily mistaken for other issues. Below are examples of how HS typically appears in its early stages.

Section Three – A Super Deep Dive into HS and its causes.
(Pour yourself a strong coffee…)

What HS is, according to current research.

What we do know about HS is this: HS is a long-term inflammatory skin disease and the most up-to-date research suggests that the cause is multifactorial. That means it develops from several internal systems interacting, rather than one single cause.

Think of your body as a complex, interconnected house. When a house starts to develop deep, structural issues, it is rarely down to one isolated incident, like a single broken window. Instead, it is a combination of underlying factors—faulty wiring, blocked plumbing, and creeping damp—all feeding into one another to cause a much larger problem. HS works in exactly the same way.

Over recent years, several areas of research have given us a much clearer understanding of some of these interconnected systems. Below, we break down these core factors. For those with a more curious nature we have provided links to the published research articles so you can read the full papers, should you wish.

We’ve worked hard to trawl the net to find published papers, read them, digested them and break them down for you on this page. We’ve tried to cover this topic comprehensively without intending to overwhelm anyone. To do this, we’ve put everything we have found into 7 contributing factors. There may well be more, but this page leans heavily on medical publications and published research, so do not take this information page to be an exhaustive list.

We know more now in 2026 than we have ever known about HS, yet we also recognise that there is an enormous amount of work still to be done before we can conclusively say what causes HS.

The Factors

1. Genetics: The Underlying Wiring

You aren’t just “unlucky.” Research now confirms that HS has a strong genetic component, meaning your DNA plays a significant role in your predisposition to the condition. Think of it as your body’s factory settings.

Does HS run in the family?
Yes, it frequently does. Studies show that around one-third of people with HS report a family history of the condition. If you have HS, it is common to wonder about the risk to your children or other relatives.

• How it is inherited: In some families, HS can appear to follow a pattern called Autosomal Dominant inheritance, especially when specific gene variants (like NCSTN or PSEN1) are involved. This means that if one parent carries a specific genetic mutation, there is a chance it can be passed directly to their children. However, for most people, HS is not explained by a single inherited gene. Instead, it is usually polygenic, meaning it’s the result of many small genetic variations interacting with one another.
• Important nuance: Inheriting the marker does not guarantee you will develop the symptoms, but it does mean your body is “wired” to be more sensitive to the triggers that cause HS to flare. (More Information: MedlinePlus)

The Fuse Box: The Gamma-Secretase Complex

Think of your genetics as the original electric wiring of your house. Most people are born with “standard” wiring that handles stress, friction, and hormones without a hitch. However, research has identified that many people with HS have variations in a group of proteins called the gamma-secretase complex.

This complex acts like the automated control system for how your hair follicles grow and how your skin cells renew themselves. When this specific wiring is faulty, it acts like a frayed wire behind the walls—it is unstable and prone to “sparking,” triggering a cascade of inflammation that the body then struggles to switch off (Deep dive: PMC8491499)

Why it’s “Polygenic” (Not just one “bad” gene)

It is tempting to look for a single faulty wire that causes HS, but the reality is more nuanced. HS appears to be polygenic, meaning it is usually the result of multiple small genetic variations interacting with one another, rather than one single major fault.

This is why two people in the same family might both carry the genetic predisposition for HS, yet one might have mild symptoms while the other experiences severe, stage-three disease. Other factors—such as your unique environment and immune response—interact with the underlying wiring issues to determine how the disease actually shows up in your life. (Recent evidence on genetic pathways: PMC10886623)

3. The Follicle: The Blocked Pipes

We have moved past the old, simplified myth that HS is just a clogged pore or a hygiene failure. Modern clinical research shows that the story of HS really begins deep within the hair follicle itself. Think of each follicle as a tiny, specialised pipe in your house’s plumbing. In a healthy system, this pipe allows hair and natural oils to exit freely. In HS, however, the cells lining this pipe—known as keratinocytes—don’t behave the way they should.

Think of it like a pipe that is being choked from the inside.
These cells produce an abnormal build up of keratin (the protein that forms hair and skin). This process, known as follicular hyperkeratosis, means the pipes walls become thickened, narrow, and incredibly fragile. (Clinical reference: PMC9326614)

As the blockage builds, pressure mounts beneath the surface. Eventually, the follicle wall—already weakened—can no longer withstand the internal force, leading to a follicular rupture. When this happens, it bursts, spilling the contents of the follicle—oils, bacteria, and dead cell debris—directly into the surrounding, delicate skin tissue. (Clinical reference: PMC9368759)

This rupture is the ground zero of an HS flare. It’s not just a surface breakout; it’s an internal spill that triggers that massive immune “smoke alarm” response we described earlier. By the time you feel that painful, throbbing lump, your body is already fighting to contain an internal rupture that has turned the surrounding area into an inflammatory battleground.(Clinical reference: PMC8361883)

5. The Hormones: The Water Pressure

Let’s be honest: metaphors are helpful for visualizing complex ideas, but human biology is far more intricate than any plumbing system. Hormones are vital, life-giving signals for your entire body—they don’t just “cause” disease. However, when we are trying to understand why HS flares happen when they do, thinking about hormones as “water pressure” is a very effective way to picture what is happening in your skin.

Think of your hormones as the mains water pressure running through your house. Under normal conditions, a healthy system handles the flow easily. But for those with HS, the “pipes” (your hair follicles) are often structurally compromised. When your body experiences natural hormonal shifts—around puberty, or worsens during pregnancy, or your monthly cycle—the “pressure” in the system rises. It doesn’t break a healthy pipe, but it pushes your compromised system to its limit, forcing the existing weak points to finally give way.

It’s about cellular sensitivity, not just levels.
The research indicates that it’s not necessarily that your hormone levels are “abnormal,” but rather that your skin cells are hyper-sensitive to them. Studies have shown that HS skin cells (fibroblasts) can show increased androgen receptor expression, meaning they react more aggressively to circulating hormones like DHT than healthy skin cells would. This reaction adds fuel to the fire, amping up the inflammation we see in the follicles (Clinical reference: PMC6551033)

While the exact interplay is still being mapped, the clinical evidence is clear: HS often begins around puberty—alongside menstrual flares, which strongly confirms that hormones are a central part of the HS puzzle. (Clinical reference: PMC8467309)

By viewing hormones as a pressure gauge, we can better understand why treatments that modulate the endocrine system (like certain contraceptives or anti-androgen therapies) provide relief for some patients, even when their blood tests appear “normal.” It isn’t about fixing a hormone imbalance; it’s about reducing the pressure on a system that is currently overreacting.

7. The Metabolic Amplifier: The House’s Central Power System

Beyond the mechanical triggers and genetics, recent research has identified a consistent link between HS and metabolic health. It is critical to understand that this is not about “blaming” an individual’s lifestyle. Instead, it is about how the body’s central “power supply” influences the overall inflammatory state of the entire house.

Think of metabolic health as the energy efficiency of your home.
If the immune system is the “smoke alarm” and the ruptured follicle is a “burst pipe,” your metabolic state—how your body processes insulin and glucose—acts as the central power system. When this system is running efficiently, everything stays stable. But when your body struggles to manage insulin effectively, the power supply becomes “dirty” or inefficient. It pumps excess heat and “static” (pro-inflammatory signals) into every room of the house. (Clinical reference: BJD 2015)

The Adipokine Cascade
Adipose (fat) tissue is not just a storage unit; it is a biologically active organ. In HS, this tissue often becomes a significant source of adipokines—signalling molecules that ramp up inflammation. These signals don’t stay in one area; they travel through your system, creating a state of “whole-house” stress. This explains why HS is so often linked to other metabolic conditions; the underlying inflammation is affecting the system’s ability to remain calm, not just the skin on the surface. (Clinical reference: PMC10886623)

The Insulin/Hormone Feedback Loop
New research into insulin-glucose homeostasis has revealed a direct link between insulin resistance and HS severity. When your body struggles to manage insulin, it can cause a spike in your ‘water pressure’ (the hormonal signals we discussed earlier), which in turn feeds the very skin cells that are prone to rupturing.

Basically, everything in the house is connected. Your metabolic system and your hormonal ‘water pressure’ work together. When one is under strain, it places a burden on the other. By understanding that HS is this ‘whole-house’ event, we can stop looking for one single ‘broken wire’ and start looking at how to settle the entire system down. (Clinical reference: PMC11990022)