Synopsis
Diagnose perineal hidradenitis, measure inflammatory activity separately from permanent tunnels and select supported medical and surgical treatment with objective follow-up.
- HS combines typical recurrent inflammatory nodules, abscesses or tunnels with a typical flexural distribution; the 2026 guideline uses at least two lesions or episodes in six months as the recurrence criterion.
- Assess acute infection separately and arrange urgent source control when needed; do not start anti-TNF treatment through uncontrolled local infection, abscess-related sepsis or active TB.
- IHS4 equals inflammatory nodules plus twice the abscess count plus four times the draining-tunnel count: at most 3 is mild, 4–10 moderate and at least 11 severe.
Key red flags
Rapidly progressive pain or systemic illness can represent superimposed infection rather than an ordinary inflammatory flare.
A persistent ulcer, enlarging mass or new bleeding in a chronically affected perineal area requires assessment and possible biopsy.
Perianal tunnels accompanied by diarrhoea, weight loss or rectal inflammation require assessment for coexisting Crohn disease.
Severe distress, hopelessness or suicidal thoughts need direct assessment and appropriate urgent support.
Investigation priorities
Confirm the pattern and establish an objective inflammatory and structural baseline.
Management branches
A 29-year-old woman has recurrent painful groin and perineal nodules without draining tunnels.
- Examination finds three inflammatory nodules and no abscess or draining tunnel, giving IHS4 = 3, mild inflammatory disease. She reports repeated flares despite an adequate topical course. There is no spreading infection, bowel symptom or suspicious ulcer; the clinician records pain at 6/10 and the effect on sitting at work.
- After confirming no tetracycline allergy, pregnancy or breastfeeding, reviewing hepatic risk and interacting medicines, she chooses the PCDS July 2025 adult regimen: doxycycline 200 mg orally once daily, using two selected 100 mg capsules, initially for three months. She takes it upright with plenty of water, well before bedtime, and receives explicit advice on sun reactions, swallowing pain and significant diarrhoea.
Key medicines
Clindamycin 1% — Dalacin T 10 mg/mL topical lotionSelected adult off-label HS use for mild-to-moderate superficial disease without draining tunnels: shake and apply a thin film to affected external skin twice daily during a flare, for up to 12 weeks under the European treatment guidance, then assess benefit and need. The selected UK product is licensed for acne, not HS.Do not use with clindamycin/lincomycin or excipient allergy, a history of inflammatory bowel disease or antibiotic-associated colitis. Stop for significant or prolonged diarrhoea and assess possible colitis even though application is topical. Avoid eyes, mucosa and intrarectal use; local irritation can occur. Review neuromuscular-blocking medicines and use caution in atopic patients. First-trimester use is only if clearly needed; pregnancy and breastfeeding require individual benefit–risk discussion, including possible infant diarrhoea, blood in stool or rash. The topical SmPC supplies no renal/hepatic adjustment schedule; do not invent one or extend an adult HS regimen to children.
Doxycycline — Sovereign 100 mg oral capsulesSelected adult off-label HS regimen from PCDS July 2025: 200 mg orally once daily, initially for three months, then review lesions and consider a treatment break if improved. Use two 100 mg capsules with plenty of water while sitting or standing, well before retiring; food may reduce gastric irritation. HS use and course come from the clinical pathway, not the product’s acne indication.Contraindicated in pregnancy, breastfeeding and tetracycline or excipient hypersensitivity. This is an adult HS regimen; do not extrapolate to a child. No renal dose adjustment is required at usual recommended doses, but hepatic impairment or other hepatotoxic medicines require caution and review. Avoid systemic retinoids such as isotretinoin because of intracranial-hypertension risk. Separate iron, zinc, bismuth and aluminium/calcium/magnesium-containing antacids as far as practical; monitor warfarin anticoagulation and ciclosporin if co-prescribed, and review enzyme inducers such as carbamazepine or phenytoin. Avoid methoxyflurane coadministration. Stop and seek assessment for severe rash, photosensitivity, significant diarrhoea or swallowing pain; headache with visual disturbance needs urgent assessment for raised intracranial pressure. Review myasthenia gravis and lupus risks before treatment.