What Is Hidradenitis Suppurativa?

In Short

Hidradenitis suppurativa is the term commonly used in the medical literature for the condition often called Acne Inversa in German-speaking countries. The abbreviation HS refers to the same condition.

HS is a chronic inflammatory skin condition. It can cause painful nodulesNodule: A firm, palpable lump deep in tissue. Nodules can be painful and may progress to abscesses. They are among the typical early signs of Acne Inversa.NoduleA firm, palpable lump deep in tissue. Nodules can be painful and may progress to abscesses. They are among the typical early signs of Acne Inversa.Read more in the glossary, abscessesAbscess: An inflamed cavity or swelling containing pus or fluid. In hidradenitis suppurativa, abscesses can form as part of the inflammatory disease process and do not automatically mean that a bacterial infection is present. Secondary bacterial infection can occur and may require separate medical assessment. In Acne Inversa, abscesses occur mainly in the armpits, groin, and other skin folds.AbscessAn inflamed cavity or swelling containing pus or fluid. In hidradenitis suppurativa, abscesses can form as part of the inflammatory disease process and do not automatically mean that a bacterial infection is present. Secondary bacterial infection can occur and may require separate medical assessment. In Acne Inversa, abscesses occur mainly in the armpits, groin, and other skin folds.Read more in the glossary, weeping areas, tunnelsSinus Tract: A tunnel-like channel under the skin that forms between abscesses or nodules. Sinus tracts indicate more advanced disease and can chronically drain fluid. They are associated with Hurley Stages II and III.Sinus TractA tunnel-like channel under the skin that forms between abscesses or nodules. Sinus tracts indicate more advanced disease and can chronically drain fluid. They are associated with Hurley Stages II and III.Read more in the glossary, and scarring. Typical regions include the armpits, groin, genital and perineal area, buttocks, or skin folds under the breasts.

The Key Points at a Glance

• HS is not contagious and is not caused by poor hygiene.
• The condition is not defined by a single symptom, but by a pattern.
• This pattern combines typical lesions, typical body sites, and recurrence.
• Other causes can look similar. A medical examination remains important.

Why Are There Several Names?

The names emphasize different aspects. “Acne Inversa” is historically widespread, but it can be misleading because HS is not simply ordinary acne occurring at a different body site. “Hidradenitis suppurativa” is internationally established, but may initially sound unfamiliar to many patients.

For conversations with your care team, it’s important to know: when findings, studies, or patient materials mention HS, Hidradenitis suppurativa, or Acne Inversa, they are generally referring to the same condition.

How Can HS Present?

HS does not always begin with the full picture of tunnels and scars. Early symptoms may resemble single deep nodules, “boilsBoil (Furuncle): Patient-community term for an inflammatory nodule or abscess. Important caveat: an ordinary single boil (furuncle) is a one-off bacterial hair-follicle infection. The recurring, multifocal 'boils' of Acne Inversa are not the same thing — this misdiagnosis is a main reason HS goes unrecognised for years.Boil (Furuncle)Patient-community term for an inflammatory nodule or abscess. Important caveat: an ordinary single boil (furuncle) is a one-off bacterial hair-follicle infection. The recurring, multifocal 'boils' of Acne Inversa are not the same thing — this misdiagnosis is a main reason HS goes unrecognised for years.Read more in the glossary,” or recurring ingrown hairs. Over time, a pattern may become noticeable:

• Nodules recur at the same or several typical sites.
• The lesions are deep, tender, or very painful.
• Areas may open up and dischargeDischarge / Exudate: Fluid coming from an Acne Inversa lesion or tunnel. Can be clear (serous), bloody (sanguineous), pus-like (purulent), or a mix.Discharge / ExudateFluid coming from an Acne Inversa lesion or tunnel. Can be clear (serous), bloody (sanguineous), pus-like (purulent), or a mix.Read more in the glossary fluid.
• After inflammation, scars, hardened cords, or tunnels remain.

This pattern is more important than a single photo or a single acute day. It also explains why a lesion that has healed by the time of an appointment does not mean the history is unimportant.

Which Features Belong in the Medical Assessment

The German guideline describes diagnosis mainly as a clinical assessment. Examination and medical history bring together three questions:

Question	What it means
Which lesions are present?	for example, inflammatory nodules, abscesses, tunnels, or scars
Where do they occur?	for example, axillary, inguinal, genital, perineal, or submammary
How does it progress?	recurrence, persistence, and changes between flaresFlare: A period of acute worsening in a chronic condition. In Acne Inversa, a flare may be triggered by stress, hormonal changes, friction, or other factors and can manifest as new nodules, abscesses, or increased pain.FlareA period of acute worsening in a chronic condition. In Acne Inversa, a flare may be triggered by stress, hormonal changes, friction, or other factors and can manifest as new nodules, abscesses, or increased pain.Read more in the glossary

This assessment protects in both directions. It helps ensure HS is not overlooked in a recurring, typical course. But it also prevents every painful spot in a skin fold from automatically being labeled HS.

What HS Is Not

HS is not contagious. It is also not a sign of poor hygiene. Knowing both is medically and personally important, because false blame can make the path to care unnecessarily difficult.

HS is also not the same as Acne vulgaris. The similar name should not obscure the fact that these conditions are described and assessed differently. If a lesion is new, appears in an unusual location, or worsens acutely, treating clinicians need to consider other causes as well.

Why the Term Matters for Diagnosis

Knowing the name allows for a more precise description of what is happening: recurring nodules, typical body regions, pain, discharge, scarring, and the impact on daily life. These clinical patterns are exactly what help with assessment.

A brief record of the course can be more helpful than searching for the perfect medical wording. Note the body site, recurrence, pain, discharge, scarring, and limitations in sitting, walking, arm movement, sleep, or clothing.

When to Seek Medical Help

If painful nodules or abscesses repeatedly occur in the armpits, groin, breast fold, genital area, or buttocks, a dermatologyDermatology: The medical specialty concerned with diagnosing and treating skin conditions. Acne Inversa is often managed by dermatologists, although surgery and other specialties may also be involved.DermatologyThe medical specialty concerned with diagnosing and treating skin conditions. Acne Inversa is often managed by dermatologists, although surgery and other specialties may also be involved.Read more in the glossary consultation is worthwhile. Early assessment can help prevent many individual acute episodes from being treated without recognizing their common connection.

If fever, rapid worsening, sharply increasing redness, or very severe pain occurs, medical evaluation should happen promptly.