Hidradenitis suppurativa (sometimes known as acne inversa) is a painful long-term skin disease that causes abscesses and scarring on the skin – usually around the groin, buttocks, breasts and armpits.
It's not known exactly what causes hidradenitis suppurativa (HS), but the disease is linked to inflamed apocrine sweat glands and plugging of the hair follicles.
The apocrine sweat glands are found in places where we have the most hair follicles, which would explain why the skin in the groin and armpits is particularly affected. See the Causes section below for more information.
An estimated 1% of the population has HS, but this may be an underestimate as some people may be too embarrassed to seek diagnosis and treatment.
What are the symptoms?
HS ranges from mild to severe.
It causes a mixture of red boil-like lumps, blackheads, cysts, scarring and channels in the skin that leak pus. These lumps and spots are found around the groin and armpits and sometimes under the breasts and in other areas (see below). HS may sometimes be mistaken for acne, folliculitis (inflammation of the hair follicles) or sexual diseases such as herpes.
Some of the lumps may become infected with bacteria, causing a secondary infection that will require antibiotics to treat. HS is very painful.
The disease tends to start with a firm pea-sized nodule (0.5-1.5cm) developing in one place, which either goes away on its own or ruptures after a few hours or days to ooze pus. This 'lesion' may return time and time again.
New lumps will often soon appear in an area nearby. If these are not controlled with medication, larger golfball-sized lumps may form and spread, and sinus tracts may develop. Sinus tracts are narrow channels under the skin that open up in the skin surface and leak pus.
This cycle continues and new lumps may continue to reappear. HS is a lifelong condition that requires constant management (see Outlook section below).
Stages of the disease
Doctors classify the disease into three distinct stages:
- Stage 1 – single or a few isolated abscesses without scarring or sinus tracts.
- Stage 2 – recurrent abscesses in more than one area and the beginning of the formation of sinus tracts.
- Stage 3 – widespread abscesses with many interconnected sinus tracts under the skin. There may be severe scarring and continuous leaking.
Main affected areas
HS usually affects skin in the following areas:
- around the groin and genitals
- in the armpits
- around the bottom (anus)
- on the buttocks and inner thighs
- below the breasts
The abscesses may spread to the nape of the neck, waistband and inner thighs. Other isolated areas have been known, including the front or back of the legs, the sides, the back area and even the face.
Many people with HS develop a pilonodal sinus, which is a small hole or 'tunnel' in the skin usually at the top of the buttocks, where the buttocks separate.
What are the causes?
The exact cause of HS is not clear, but the bumps and spots appear to be the result of blocked apocrine sweat glands and hair follicles.
Sweat becomes trapped inside the tubes from the sweat glands, which swell up and either burst or become severely inflamed (see Symptoms section above).
However, the disease is not infectious and it is not caused by an infection. It is not linked to poor hygiene.
It is thought that HS may be caused by a problem with the immune system. According to the British Association of Dermatologists, the disease may be linked to Crohn's disease. Many HS patients also suffer from another underlying autoimmune disorder (where the immune system attacks the body's own cells and tissues).
Who is affected?
HS usually starts around the age of puberty, but it can appear at any age.
It is less common for HS to occur before puberty or after the menopause, leading some experts to believe that the sex hormones have some sort of influence on the disease.
Sometimes, HS runs in families.
HS affects three times more women than men, for reasons that are not clear.
Many people with HS:
- are smokers
- are overweight
- also have hirsutism (excessive hair growth) and/or acne, both of which are linked to levels of sex hormones
Smoking and being obese are likely to make the condition worse.
It's recommended that you lose any excess weight and stop smoking if you smoke – this can lead to an improvement in symptoms within several months.
It may help to wear loose-fitting clothes to reduce friction against your skin. Avoid shaving the skin and wearing perfume or perfumed deodorants in the affected area.
It's also a good idea to use antiseptic soap or an antiseptic wash to reduce skin bacteria (try 4% chlorhexidine wash), and to hold a warmed flannel to the spots to encourage the pus to drain.
Many people with HS benefit from joining a local support group – ask your doctor for details of your nearest one, or contact The Hidradenitis Suppurativa Trust.
How is it treated?
HS can be difficult to manage. The aim is to catch the disease in its early stages and prevent it getting worse. Therefore an early diagnosis is important.
In the early stages, the disease may be controlled with medication. Persistent and severe cases may require surgery. These treatments are outlined below.
If your lumps are particularly painful, red and oozing pus, your GP or specialist may prescribe a two-week course of antibiotic tablets, as there may be a secondary infection present.
You can also try anti-acne antibiotic creams such as clindamycin or erythromycin, to use alongside benzoyl peroxide wash (a gel to help unblock the glands).
Some people may need a longer course of antibiotics to bring symptoms under control. For example, you may be prescribed a combination of rifampicin and clindamycin for two to three months if your HS is severe. This brings remission (a symptom-free period) for most patients.
You may also be tried on penicillin treatments such as flucloxacillin, amoxicillin or co-amoxiclav.
The above links will take you to more information on these drugs, including side effects and how you should use them.
You may be prescribed steroid medicine (corticosteroids) such as prednisolone to reduce severely inflamed skin. Corticosteroids can be taken as tablets, or you may have an injection of the drug directly into your affected skin.
Possible side effects of corticosteroids are fluid retention, weight gain, constipation and mood swings. Find out more about the side effects of corticosteroids.
Retinoids are vitamin-A based drugs such as isotretinoin. They are not as effective for HS as they are for acne, but a course for six-12 months may help to control some of the spots and lumps.
Isotretinoin should be used with caution, with the advice of a specialist. It cannot be taken during pregnancy and possible side effects include dry lips, skin and eyes. Read more about the side effects of isotretinoin.
Women whose HS flares up before their period may benefit from taking the contraceptive pill for 12 months or more.
The pill contains an artificial version of oestrogen, which should help reduce secretions from the sweat glands and help control the lumps.
Ciclosporin is a powerful medication that suppresses the immune system. For some patients with HS, it can relieve symptoms for a few months.
However, this medicine can cause vomiting, diarrhoea, high blood pressure, numbness, and kidney and liver problems. Learn more about the side effects of ciclosporin.
Infliximab and adalimumab
Biological drugs like infliximab or adalimumab, which also suppress the immune system, may be prescribed for severe cases of HS.
These powerful drugs are very effective but expensive. Your dermatologist will usually only prescribe them if other treatments don't work for you.
Infliximab and adalimumab are given by injection at hospital or at a clinic. You may need to have the injections about every eight weeks.
Possible side effects include blood disorders, infection and tissue cancers. Speak to your doctor about these side effects if you are considering taking this medication.
A surgical procedure may be considered if your HS is not controlled with medication.
If you have some very large lumps that will not clear with antibiotics, you may be offered one of the following treatments:
- incision and drainage or removal – cutting off the lids of the lumps and draining or scraping out the contents inside, or removing the lumps altogether
- laser ablation – using a laser to remove the lumps (this has no proven benefit and is an experimental treatment)
- cryotherapy – freezing off the lumps with liquid nitrogen
HS persists for many years and there is no cure, but symptoms may be improved with treatment if it is diagnosed early.
Not all people with HS progress to stage 3 – the disease can be controlled so it doesn't progress beyond stage 1.
However, HS can affect your life in many ways. Routinely changing dressings and living with the pain, discomfort and embarrassment of the symptoms can affect quality of life and lead to depression. If you are having problems coping, speak to your health professional or a charity to see what support is available. Read about finding mental health support.