You may not give much thought to your armpits, apart from checking whether they need another swipe of deodorant. But this small, often overlooked patch of skin is one of the body's busiest crossroads. Beneath those folds lies a complex network of glands, nerves and lymph nodes that keep you cool, fight infection and even influence how you smell to others.
Author
- Dan Baumgardt
Senior Lecturer, School of Psychology and Neuroscience, University of Bristol
The armpit's design allows flexibility and free movement of the arm, while serving as a vital passageway for blood vessels and nerves that link the limb to the torso. It is also home to sweat glands that regulate temperature and release pheromones , and to clusters of lymph nodes that drain fluid and help defend the body against infection .
Yet for some people, this humble underarm becomes the site of something far more troublesome than a bit of body odour. A distressing, recurring condition called hidradenitis suppurativa (HS) can turn these hidden hollows and other areas where skin rubs together into a source of chronic pain, infection and scarring. Once thought to be rare, HS is increasingly recognised and diagnosed, though still widely misunderstood.
Several conditions can develop within the tissues of the armpit (or axilla, as it is known anatomically). One of these is the rather bewilderingly named hidradenitis suppurativa .
The name translates to "inflammation of the sweat glands with pus," and that is essentially what the condition involves. HS is a chronic condition that affects areas of the body rich in sweat glands and hair follicles, particularly where the skin folds and rubs together. This means it can appear not only in the armpits but also in the groin, around the breasts and buttocks, and in the perineal area . Friction in these regions may make the condition worse.
The inflammation appears to be driven by a process similar to autoimmunity , where the body mistakenly attacks its own tissues. It seems that blockage of the hair follicles occurs first, which then triggers involvement of the sweat glands. The condition is estimated to be nearly three times more common in women than in men and may also run in families. Other risk factors include increased levels of androgens , which are hormones such as testosterone that increase after puberty, as well as smoking and obesity .
Research also shows that people of colour are disproportionately affected. Both UK and US studies have found that HS is more common and often more severe among black and Hispanic patients. These groups are also more likely to experience delays in diagnosis or have their symptoms mistaken for other infections or boils. The reasons are complex and include differences in healthcare access, underrecognition of how HS presents on darker skin tones and broader structural inequities within medical systems. Early recognition and equitable care can help prevent advanced disease and reduce the burden of pain, scarring and stigma that HS can cause.
HS symptoms
Inflamed and blocked glands appear on the skin as hard nodules or swellings. Infection can turn these into abscesses that may grow to significant sizes. Prolonged inflammation and infection can lead to the formation of sinuses, which are tunnels beneath the skin that connect nodules, and to scarring. This can cause painful, oozing or foul-smelling skin, sometimes restricting upper limb movement if scar tissue forms.
These processes resemble those seen in acne vulgaris , which is the medical term for common acne. In fact, one of the alternative names for HS is acne inversa, referring to the inverted skin folds where it occurs. Like acne, it is not caused by poor hygiene and it is not contagious, despite common misconceptions.
When it comes to managing HS, some treatments overlap with those used for acne. Antibiotics such as lymecycline, which have both antibacterial and anti-inflammatory properties, can help prevent flare-ups. Lifestyle changes are also recommended, such as wearing loose clothing and losing weight to reduce skin folds and friction.
In some cases, HS can cause large abscesses, sometimes five to ten centimetres across, which may require surgery to drain the pus or remove scar tissue. Because of the long-term nature and scarring associated with severe disease, new biological therapies such as adalimumab, which work by calming the immune system's overreaction, are now being used to manage more advanced cases.
HS diagnoses are rising each year. This could reflect an actual increase in numbers or simply better recognition. It may seem surprising that such a condition could be so often missed or misdiagnosed, but it happens.
HS can mimic other skin conditions that affect the folds. It is common to experience irritation from sweating or shaving in the armpits or groin, leading to folliculitis , which is inflammation of the hair follicles. Because HS lesions tend to flare and then subside, sometimes improving with short-term antibiotics, they are often mistaken for other problems and treated incompletely, sometimes for years.
Historically, HS has been poorly recognised. Its variable symptoms and the embarrassment and stigma that often surrounds skin changes in intimate areas have contributed to delays in diagnosis. Early detection can prevent progression to severe disease, so any recurrent skin changes are worth discussing with a doctor.
The armpit may seem insignificant, but for those affected by hidradenitis suppurativa, it can shape daily life in painful and isolating ways. Too many people live with the condition for years before receiving a diagnosis or effective treatment. Recognising it as a medical condition rather than a hygiene problem is a crucial step in changing that.
Dan Baumgardt does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
