Hidradenitis suppurativa (HS): a patient guide to symptoms, flares and treatment

The British Association of Dermatologists describes HS as a chronic, recurrent and painful inflammatory condition. It tends to occur where apocrine sweat glands sit, mainly in the armpits, breasts, tummy fold, groin, genital area and buttocks. Within these areas hair follicles become blocked and inflamed, producing a mixture of boil-like lumps, areas leaking pus and scarring such as skin tunnels.

The NHS lists the usual sites as the groin and genitals, armpits, the bottom and around the anus, and below the breasts, with lumps sometimes on the nape of the neck, waistband and inner thighs. It adds that HS usually starts around puberty and can occur at any age afterwards; the dermatologists say it is rare before puberty and most people notice lumps in early adulthood.

The NHS says symptoms range from mild to severe. It tends to start with blackheads, pus-filled spots and firm pea-sized lumps in one place. The lumps either disappear or rupture and leak pus after hours or days, and new lumps often develop nearby. If these are not controlled, larger lumps can form and spread, and narrow channels called sinus tracts can develop under the skin and break out on the surface.

The dermatologists add that the abscesses are usually painful, that pain can make sitting or walking difficult, and that discharge may need daily dressings. In later stages, tunnels may form and wounds may not heal easily, with more scarring over time. Some lumps can become infected with bacteria, which the NHS says needs antibiotics.

The cause is not fully understood. The dermatologists say it is thought to begin with blockage of hair follicles, so fluid cannot escape and the follicle swells and bursts, causing inflammation or abscesses. They describe hormones, bacteria trapped in blocked follicles and an over-active immune system as likely contributors, and note it may be worse before periods. The NHS likewise points to blocked hair follicles and suggests sex hormones may play a part.

Smoking and weight both matter. The NHS says smoking and obesity are strongly associated with HS and make symptoms worse. The dermatologists say up to 60% of people affected are smokers, but non-smokers can have it too, and that it can affect people of normal weight but is more common in those who are overweight.

It runs in families in about 1 in 3 cases (NHS; the dermatologists say about one third). Linked conditions include acne, hirsutism, pilonidal sinus, depression and anxiety, and in some people Crohn disease or ulcerative colitis and inflammatory arthritis. The dermatologists also note links with high cholesterol, high blood pressure and diabetes, which do not cause HS but may prompt checks of weight, blood pressure, sugar and cholesterol, and advise seeking medical attention for persistent bowel symptoms or persistent joint pain or swelling.

There is no specific test. A healthcare professional examines the area and considers the history; the NHS says a swab may help because HS is not usually associated with the bacteria that cause typical skin infections. The dermatologists warn that it is often misdiagnosed at first as an infection or inflamed hair follicles, which delays treatment and allows scarring. A pattern of recurrent boil-like lumps in the same skin folds is the clue that a GP may refer to a dermatologist.

The dermatologists list steps for a sudden new painful abscess: a warm flannel or bath may encourage drainage; anti-inflammatory painkillers can help pain and inflammation; a topical steroid can sometimes reduce redness and swelling; a course of antibiotics may help; lancing and draining can reduce pain with temporary improvement; and dermatologists sometimes consider a steroid injection into the lump. The NHS suggests holding a warm flannel on lumps to encourage pus to drain. Dressings should be prescribed for people with fluid drainage.

Sensible day-to-day measures from both sources include loose-fitting clothing, avoiding tight underwear, avoiding shaving affected skin, using an antiseptic wash or soap, losing weight if overweight and stopping smoking if you smoke.

• Seek medical advice if a lump becomes very painful, hot, or you feel generally unwell, as secondary infection can need antibiotics.

• Tell your GP if low mood or anxiety develops; the NHS says the condition can lead to depression and to speak to a GP if finding it hard to cope.

The NHS says early HS may be controlled with medicine and surgery may be needed in severe or persistent cases; the dermatologists say treatment is tailored to each person, with early HS usually treated with medication and longer-standing or severe disease benefiting from medication and surgery.

Medicines named by the NHS and the dermatologists include antibiotics, either short courses for infected lumps or longer courses of at least 3 months at low dose to reduce the number of lumps (the dermatologists say these may work by suppressing inflammation rather than killing bacteria), antiseptic washes such as 4% chlorhexidine, retinoids such as acitretin (prescribed only by dermatologists and avoided if pregnancy is possible, with pregnancy avoided for 3 years after stopping), hormonal treatments for flares before periods, metformin in some people, and, for severe or hard-to-treat disease, immune-suppressing treatments. The dermatologists list biologic injections such as adalimumab, secukinumab and bimekizumab, and infliximab by infusion, for moderate to severe HS that has not improved with other treatment, with monitoring because of the risks of suppressing the immune system. Which options suit a person is a specialist decision.

For scarring and tunnels, the dermatologists say surgery is usually needed. Deroofing under local anaesthetic removes the roof of a tunnel so it heals naturally over a few weeks, while larger or deeper areas may need wider removal under general anaesthetic, which is more likely to reduce recurrence in that area but takes longer to heal. Surgery works better alongside medical treatment, and biologic therapy is usually continued, though it may be paused if non-HS internal surgery is needed.

The dermatologists say the effect of pregnancy varies: in most cases HS is unchanged or improves, but there can be more flares soon after delivery. Long-term, the NHS says HS can have a significant effect on everyday life, with dressing changes and ongoing pain affecting quality of life. The dermatologists mention patient groups including the Hidradenitis Suppurativa Support Network UK and Ireland, and suggest trying to reduce stress and anxiety.