Hidradenitis suppurativa

hidradenitis · HS · acne inversa · recurrent boils in the armpit or groin

Not recurrent boils - a chronic inflammatory disease, routinely misdiagnosed for years, and repeated incision is not the treatment.

ROUTINE DERMBand C

Red flags

Systemic sepsis or a rapidly expanding abscess on a background of hidradenitis - it can still develop an acute collection needing drainage
Perianal disease with fistulation - consider coexisting Crohn disease and involve colorectal surgery
Long-standing untreated perineal or buttock disease - squamous cell carcinoma is a recognised late complication
Depression or suicidal ideation - the psychological burden of this disease is severe and should be asked about directly

Recognise

On light skin

Painful red nodules and abscesses in the flexures, with draining sinus tracts, double-headed comedones and rope-like scarring.

On brown and black skin

Active lesions may be violaceous, dark brown or hyperpigmented rather than red, and the background post-inflammatory hyperpigmentation can make it hard to tell active disease from old damage. The structural features are what count and they are tone-independent: palpable deep nodules, sinus tracts that can be probed or that discharge on pressure, tethered rope-like scarring, and double-headed (tombstone) comedones. Two further points are clinically important. Hidradenitis is widely reported to be commoner in Black patients. No prevalence figure is cited here because none could be traced to a source read in full - treat it as a reason to raise the index of suspicion, not as a quotable statistic. And keloid and hypertrophic scarring after surgery is substantially more likely - pooled odds ratio 6.14 (95% CI 3.75 to 10.07) in Black compared with White individuals in a 2026 network meta-analysis - so the caution about repeated incision should be higher, not lower.

In any skin tone

Recurrence in the same flexural sites over months or years - this is the diagnosis, and it is what distinguishes it from a simple abscess
Bilateral involvement of axillae, groin, inframammary or perianal skin
Sinus tracts and scarring - evidence of chronicity
Double-headed comedones
Strong association with smoking and obesity, and a family history is common - no proportion is quoted here because none could be traced to a source read in full, so ask about it rather than relying on a figure
Severe pain, and a substantial burden of shame and social withdrawal that is regularly missed

Distribution

Intertriginous sites: axillae, groin, inframammary folds, buttocks and perianal skin. Characteristically bilateral and recurrent in the same places.

Photographs

Hidradenitis suppurativa in a flexure. Several deep inflammatory nodules, two of them discharging - one bloody, one with a bead of pus - set — Hidradenitis suppurativa in a flexure. Several deep inflammatory nodules, two of them **discharging** - one bloody, one with a bead of pus - set in skin that is already scarred and tethered from previous episodes. Recurrent painful lesions at this site, in this pattern, are the diagnosis; the common error is to treat each flare as a fresh isolated abscess. Hidradenitis is both commoner and more often misdiagnosed in people with black skin.
Fitzpatrick II (Fitzpatrick type estimated from the photograph, not stated by the source) · HidradenitisAwareness · Wikimedia Commons - HS Stage III.jpg · CC BY-SA 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Skin abscess, boils and folliculitis — The usual misdiagnosis. A simple abscess is a single event in one place; hidradenitis recurs in flexures and scars
Cellulitis — Flares are often treated as cellulitis; the flexural distribution and sinus tracts distinguish them

What to do in the ED

Name the diagnosis. Most patients have attended repeatedly with 'boils' for years without being told what it is, and naming it is the single most valuable thing an ED visit can do
Drain a genuine acute collection for pain relief, but understand that incision and drainage does not treat the disease and repeated wide incision causes scarring
Adequate analgesia - this is a very painful condition and is routinely under-treated
Antibiotics for an acutely infected flare per local policy, recognising that much of the inflammation is not infective
Refer to dermatology for disease-modifying treatment; there is no UK national guideline, and the European S2k guidelines are the practical reference
Offer smoking cessation and weight management support without moralising - both modify the disease
Ask about mood and about the impact on work and relationships

Disposition

ROUTINE DERM

Dermatology referral for disease-modifying treatment, with colorectal involvement for perianal disease. Admit only for systemic sepsis or a collection requiring theatre.

Safety-netting

This is a long-term condition and it is treatable, but it needs a dermatologist rather than repeated courses of antibiotics. Return sooner if you develop a fever, if an area becomes rapidly more painful and swollen, or if you feel unwell. If you are struggling with how this is affecting your mood or your life, please say so - that is a part of the condition and there is help for it.

Local variation

There is no UK national guideline for hidradenitis suppurativa; practice follows the European S2k guidelines and local dermatology services, and access to biologic therapy varies. Those guidelines are also adult-weighted - hidradenitis does begin in adolescence but paediatric disease is uncommon and should be a specialist rather than an ED-led decision.

Sources

Open this entry in the interactive tool