What Is Acne Inversa? Symptoms, Stages, and When to See a Doctor

Written by Dr. rer. nat. Dennis Alexander Kwiatkowski

Key Takeaways

• Acne inversa (hidradenitis suppurativa) is a chronic, inflammatory skin condition — not an infection and not caused by poor hygiene.
• It typically appears as painful nodules, abscesses, and tunnels in areas where skin rubs together, such as the armpits, groin, and under the breasts.
• The condition progresses through three clinical stages (Hurley stages), from isolated lumps to widespread scarring and tunnel formation.
• Early diagnosis matters. On average, people with acne inversa wait years before receiving a correct diagnosis.
• If you notice recurring painful lumps in skin-fold areas, see a dermatologist — even if previous doctors have called them boils or cysts.

A Condition With Many Names — and Too Little Awareness

Acne inversa goes by several names. In medical literature, it is most commonly referred to as hidradenitis suppurativa, often abbreviated to HS. You may also see it called acne inversa, particularly in European dermatology. Despite affecting an estimated one to four percent of the population worldwide, it remains one of the most underrecognized chronic skin diseases.

The name itself can be misleading. Acne inversa is not a form of acne. It does not arise from clogged pores the way common acne (acne vulgaris) does, and standard acne treatments are generally not effective against it. For a deeper side-by-side look at how these two conditions differ, see our complete clinical comparison of hidradenitis suppurativa vs. acne vulgaris. Understanding this distinction is one of the first steps toward getting the right care.

What Happens in the Skin

Acne inversa is rooted in chronic inflammation of the hair follicles. The process typically begins when a hair follicle in a skin-fold area becomes blocked and ruptures beneath the surface of the skin. The immune system responds with intense inflammation, leading to the formation of painful nodules and, over time, abscesses that can rupture and drain.

In more advanced cases, repeated cycles of inflammation and healing create sinus tracts — tunnels beneath the skin that connect inflamed areas to one another. Scar tissue accumulates. The result is a condition that can be deeply painful, physically limiting, and emotionally exhausting.

It is important to understand that acne inversa is not caused by poor hygiene, and it is not contagious. It is a systemic inflammatory condition with genetic, immunological, and environmental components.

Where Does It Appear?

Acne inversa has a strong preference for areas of the body where skin folds or rubs against itself. The most commonly affected areas include:

• Armpits (axillae)
• Groin and inner thighs
• Under the breasts (inframammary folds)
• Buttocks and perianal region
• Lower abdomen

Less commonly, lesions can also develop on the nape of the neck, behind the ears, or on the chest. Some people experience the condition in only one area. Others are affected in multiple regions simultaneously.

Recognizing the Symptoms

The symptoms of acne inversa can vary widely in severity, but there are patterns that are characteristic of the condition. For a focused guide on the early signs of hidradenitis suppurativa, including prodromal warning signs, see our dedicated overview.

Recurring painful lumps

The earliest and most common sign is the appearance of deep, tender nodules under the skin. These are not superficial pimples — they sit deeper in the tissue and can range from pea-sized to several centimeters in diameter. They are often mistaken for boils, ingrown hairs, or infected cysts, which is one reason why misdiagnosis is so common.

Abscesses and drainage

As the condition progresses, nodules can develop into abscesses — pockets of pus that may eventually rupture and drain. The drainage can be foul-smelling, which adds a significant psychological and social burden for many patients. Some abscesses resolve on their own; others require medical intervention.

Sinus tracts and tunnels

In more advanced disease, repeated inflammation in the same area leads to the formation of sinus tracts — channels beneath the skin surface that connect separate lesions. These tracts can drain intermittently and are often resistant to treatment without surgical intervention.

Scarring

Chronic inflammation and repeated wound healing produce scar tissue over time. In severe cases, scarring can become thick and rope-like (hypertrophic), restricting movement and causing significant discomfort.

Pain and tenderness

Pain is one of the most reported and most debilitating symptoms. It can range from a dull ache to sharp, throbbing pain that interferes with sitting, walking, or moving the arms. Many patients describe flares as among the most painful experiences they have had.

The Hurley Staging System

Dermatologists use the Hurley staging system to classify the severity of acne inversa. It is a simple, widely used framework that helps guide treatment decisions.

Hurley Stage I — Mild

Single or multiple isolated abscesses without sinus tracts or significant scarring. Lesions may come and go. Many patients at this stage have not yet received a formal diagnosis, because the symptoms can resemble common boils or folliculitis.

Hurley Stage II — Moderate

Recurrent abscesses with the beginning of sinus tract formation and scarring. Lesions may be present in more than one area, and flares tend to be more frequent. Everyday activities may become more difficult during active flare periods.

Hurley Stage III — Severe

Diffuse or widespread involvement with multiple interconnected sinus tracts, significant scarring, and chronic drainage. This stage often has a profound impact on mobility, daily life, and mental health. Surgical options are frequently discussed at this stage.

A note on staging

The Hurley system is useful but has limitations. It captures a snapshot of disease severity but does not fully reflect how the condition affects a person’s quality of life. Two patients at the same Hurley stage can have very different experiences depending on pain levels, flare frequency, location of lesions, and psychological impact. Newer assessment tools, such as the International Hidradenitis Suppurativa Severity Score System (IHS4), aim to capture these nuances more precisely.

Who Is Affected?

Acne inversa can develop in anyone, but certain groups are more frequently affected.

• Age of onset: Symptoms most often begin after puberty, typically between the late teens and early thirties. It is rare before puberty and less common after menopause.
• Sex: The condition is more frequently diagnosed in women, though men can also be affected and may be more likely to develop perianal or gluteal disease.
• Family history: There appears to be a genetic component. Having a first-degree relative with acne inversa increases the likelihood of developing the condition.
• Smoking and body weight: Both tobacco use and higher body mass index are associated with more severe disease, though they are not considered direct causes.

What Triggers Flares?

Flare patterns vary from person to person, but commonly reported triggers include:

• Friction and pressure from tight clothing or prolonged sitting
• Heat and sweating, especially in warm weather or during exercise
• Hormonal changes, including menstrual cycles
• Stress, both physical and emotional
• Certain foods, though evidence on dietary triggers remains limited and individual responses vary

It is worth noting that identifying personal triggers can take time and often involves careful self-observation. What triggers a flare in one person may have no effect on another. Along the way, it can also help to separate fact from fiction — our overview of 10 acne inversa myths that need to go addresses some of the most persistent misconceptions.

Why Diagnosis Takes So Long

One of the most frustrating aspects of acne inversa is the diagnostic delay. Studies have found that the average time from first symptoms to a confirmed diagnosis can range from seven to ten years or more. There are several reasons for this, which we explore in more detail in our guide to recognizing hidradenitis suppurativa before it progresses.

Many general practitioners are not familiar with the condition, particularly in its early stages. The lumps and abscesses that characterize early acne inversa can easily be mistaken for recurrent boils, folliculitis, or infected cysts. Patients are often treated with repeated courses of antibiotics or referred for individual abscess drainage without anyone recognizing the underlying pattern.

Embarrassment also plays a role. Because acne inversa frequently affects intimate areas of the body and can involve odor and drainage, many people delay seeking help or avoid discussing their symptoms fully.

When to See a Doctor

If any of the following apply to you, it is worth making an appointment with a dermatologist — ideally one with experience in inflammatory skin conditions:

• You have recurring painful lumps in your armpits, groin, under the breasts, or buttocks that keep coming back in the same areas.
• You have been told you have chronic boils or recurrent abscesses, but treatment has not resolved the problem.
• You notice tunnels or channels under the skin that drain fluid or pus.
• You have scarring in skin-fold areas that seems to be getting worse over time.
• Your symptoms are affecting your daily life, your ability to work, your relationships, or your mental health.

You do not need to wait until the condition is severe to seek a diagnosis. In fact, earlier diagnosis and treatment can help slow progression and improve quality of life.

What to expect at the appointment

A dermatologist can usually diagnose acne inversa based on a clinical examination and a detailed history of your symptoms. There is no single blood test or biopsy that confirms the diagnosis — it is based on the pattern of recurring inflammatory lesions in characteristic locations. Bringing a record of your flare history, including where lesions appear and how often they return, can be very helpful.

Living With Acne Inversa

Receiving a diagnosis can be both difficult and validating. Many patients describe a sense of relief at finally having a name for what they have been experiencing, even as they come to terms with the chronic nature of the condition.

There is currently no cure for acne inversa, but there are treatments that can reduce flare frequency, manage pain, and improve quality of life. These range from topical and systemic medications to biologic therapies and surgical procedures. Treatment plans are highly individual and are best developed in partnership with an experienced dermatologist.

Beyond medical treatment, many people with acne inversa find that wound care strategies, clothing choices, lifestyle adjustments, and mental health support all play an important role in managing the condition day to day. You are not alone in this — and you do not have to figure it out without help.