Hidradenitis suppurativa !
Hidradenitis suppurativa causes painful lumps, abscesses and draining tunnels in the armpits, groin and skin folds. It is not caused by poor hygiene.
Updated 2026-11-01
Structures involved
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Why it happens
- Chronic inflammation: causes, cells and features
- Outcomes of acute inflammation: resolution, abscess, scar or chronic inflammation
- Hair follicles, sebaceous and sweat glands, nails
What it is
A chronic, recurrent inflammatory disease of the hair follicle (follicular occlusion) affecting apocrine gland-bearing skin of the axillae, groin, perineum, buttocks and under the breasts. It causes deep painful nodules, abscesses, sinus tracts (tunnels) and scarring.
Who gets it
Affects about 1% of people, more often women, starting after puberty, usually in the 20s; more frequent in people with obesity and in smokers. It is underdiagnosed and often mistaken for recurrent boils, with long delays to diagnosis.
Causes
- Occlusion of the hair follicle with rupture and an inflammatory reaction, not a primary infection
- Immune dysregulation (IL-17, TNF-alpha and IL-1 pathways)
- Genetic predisposition (family history in about a third; gamma-secretase gene mutations in some families)
- Hormonal influence, with flares around menstruation
Risk factors
- Smoking
- Obesity and metabolic syndrome
- Family history
- Female sex, puberty to middle age
- Friction from tight clothing; polycystic ovary syndrome and Crohn disease
Pathophysiology
Follicular hyperkeratosis plugs the hair follicle, which dilates and ruptures, spilling keratin and bacteria into the dermis. This triggers a strong innate and Th17 immune response with neutrophils, forming painful nodules and abscesses. Repeated cycles create epithelialised sinus tracts and dense scar tissue, which keep inflammation going.
Classification
- Hurley stage I: isolated abscesses without sinus tracts or scarring
- Hurley stage II: recurrent abscesses with sinus tracts and scarring, separated by normal skin
- Hurley stage III: diffuse involvement with interconnected tracts across the whole area
Symptoms and signs
- Recurrent painful, deep nodules in the armpits, groin, inner thighs, buttocks or under the breasts
- Abscesses that rupture and drain foul-smelling pus or blood
- Sinus tracts (tunnels) that drain chronically
- Double-ended comedones (tombstone blackheads)
- Rope-like scarring and restricted movement
- Major impact on quality of life, sleep, work and mood
Diagnosis
- Clinical
- Clinical: typical lesions (deep nodules, abscesses, tunnels, scars), typical sites, and recurrence (at least twice in 6 months). Stage with Hurley.
- Tests
- No specific test. Culture only if secondary infection is suspected; screening for diabetes, lipids and other comorbidities; biopsy for atypical or non-healing lesions.
- Imaging
- Skin ultrasound shows the extent of tunnels and fluid collections and helps plan surgery; MRI for complex perineal disease.
Differential diagnosis
- Furuncles and carbuncles (Staphylococcus aureus)
- Infected epidermoid cyst
- Pilonidal disease
- Crohn disease with perianal or cutaneous fistulas
- Lymphogranuloma venereum, scrofuloderma (cutaneous tuberculosis), actinomycosis
Goal of treatment
Reduce flares, pain and drainage, stop progression to tunnels and scars, treat comorbidities and support quality of life; treatment escalates with Hurley stage.
Treatment
- Lifestyle
- Stopping smoking, weight loss, loose clothing, gentle cleansing and wound care; pain control and psychological support.
- Medical
- Mild disease: topical clindamycin and antiseptic washes; intralesional corticosteroid for acute painful nodules.
- Medical
- Moderate disease: oral tetracyclines, or clindamycin with rifampicin; hormonal therapy or metformin in selected women.
- Medical
- Moderate to severe disease: biologic agents (TNF-alpha inhibitors such as adalimumab, IL-17 inhibitors such as secukinumab).
- Surgical
- Deroofing of tunnels, local excision, or wide excision of the affected area in Hurley III; simple incision and drainage gives only short relief.
Drugs for this condition
Complications
- Extensive scarring and contractures limiting arm or leg movement
- Chronic pain, depression, anxiety and social isolation
- Secondary infection and, rarely, sepsis
- Lymphoedema of the genitals or limbs
- Squamous cell carcinoma in long-standing gluteal or perineal disease
- Anaemia of chronic inflammation; association with spondyloarthritis
Prognosis
Chronic and relapsing; early diagnosis and treatment can slow progression. Advanced disease usually requires biologics and surgery. Smoking and obesity worsen the course.
Test yourself
Think of the answer, then tap the question to see it.
Is hidradenitis suppurativa primarily an infection?
No; it is a chronic inflammatory disease of follicular occlusion, although secondary infection can occur.
Which two modifiable risk factors are most strongly linked to hidradenitis suppurativa?
Smoking and obesity.
What staging system is used for hidradenitis suppurativa?
The Hurley staging system (I to III), based on tunnels and scarring.
Which biologic class is approved for moderate to severe hidradenitis suppurativa?
TNF-alpha inhibitors (adalimumab); IL-17 inhibitors are also used.
Which cancer can arise in long-standing perineal or gluteal hidradenitis?
Squamous cell carcinoma.
Related conditions
- Obesity
- Metabolic syndrome
- Type 2 diabetes mellitus
- Polycystic ovary syndrome
- Crohn disease
- Acne vulgaris
- Pilonidal disease
- Cutaneous squamous cell carcinoma
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Hidradenitis Suppurativa (MedlinePlus, US National Library of Medicine, 2026); Hidradenitis suppurativa: Overview (American Academy of Dermatology, 2026).
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