Hidradenitis suppurativa (HS) is a chronic skin condition that causes painful lumps, abscesses, and sometimes tunnels beneath the skin, primarily in areas where skin rubs together. It affects roughly 1% of the global population, and because early lesions look a lot like pimples or boils, the average person goes about 10 years from first symptoms to a correct diagnosis.
What Early HS Looks and Feels Like
The first sign of HS is usually a deep, firm nodule under the skin, typically 0.5 to 2 centimeters across. These lumps sit deeper than a regular pimple and tend to form in the armpits, groin, inner thighs, under the breasts, or around the buttocks. They’re painful to the touch, slow to heal, and often come back in the same spots.
About half of people with HS notice warning signs 12 to 48 hours before a new lump appears: burning, stinging, itching, warmth, or excessive sweating in the area. These prodromal symptoms can help you distinguish an incoming HS flare from a random pimple or ingrown hair.
Early lesions are frequently mistaken for boils or infected hair follicles. The key difference is the pattern. A boil typically shows up once, drains, and heals. HS lumps recur in the same locations, persist for days to months, and tend to multiply over time. You may also notice small pitted areas of skin with blackheads, often appearing in pairs. These “double-barreled” comedones are a hallmark of HS that ordinary acne doesn’t produce.
Pain During Flares
Pain is the symptom that drives most people to seek help, and it can be severe. On a 1-to-10 scale, people with HS report an average pain level of about 2.5 on a typical day. During an active flare, that jumps to an average of 7.6. More than half of patients rate flare pain at 8 or higher, and nearly a quarter report a 10, the worst pain imaginable.
One counterintuitive finding: pain severity during flares doesn’t correlate with how advanced the disease looks on the surface. Someone with a single recurring abscess can experience the same intensity of pain as someone with widespread scarring and tunneling. This means early-stage HS can be just as debilitating as later stages in terms of what you actually feel.
Drainage and Odor
As nodules grow, they often rupture or drain on their own, releasing fluid that ranges from blood-tinged to thick pus. This drainage can stain clothing and carry a strong, unpleasant smell. The odor comes from bacteria on the skin breaking down sweat, gland secretions, and dead cells into volatile organic compounds. It’s not a hygiene issue, but many people with HS describe the smell as one of the most distressing parts of the condition, affecting their willingness to be in social situations or intimate relationships.
How Symptoms Progress Over Time
HS is classified into three stages, known as Hurley stages, based on what’s happening beneath and on the skin.
- Stage I: One or more abscesses without scarring or tunnels under the skin. Flares come and go, and the skin between episodes may look completely normal.
- Stage II: Recurring abscesses with sinus tracts (tunnels connecting lesions under the skin) and scarring. Patches of normal skin still separate the affected areas.
- Stage III: Widespread involvement with multiple interconnected tunnels and abscesses, leaving little or no normal skin in the affected region.
The tunnels that define later-stage HS form when repeated inflammation damages the tissue around hair follicles. The structural lining where oil glands meet the hair follicle breaks down, allowing inflammation to spread sideways under the skin. Bacteria then colonize these channels in sticky clusters called biofilms, making infections harder to clear and encouraging the tunnels to persist. Over time, the surrounding tissue scars and thickens, which is why advanced HS areas can feel ropy or hard to the touch.
Not everyone progresses through all three stages. Many people remain at Stage I for years or indefinitely, especially with early treatment.
Where HS Typically Appears
HS targets skin folds where friction, heat, and moisture create the right conditions for follicle blockages. The most common locations are the armpits, groin and inner thighs, under the breasts, between the buttocks, and around the waistband area. Some people develop lesions in less typical spots like behind the ears or on the nape of the neck. The distribution can differ between men and women: groin and perianal involvement is more common in men, while women more often experience lesions in the armpits and under the breasts.
Symptoms Beyond the Skin
HS isn’t purely a skin disease. The chronic inflammation driving those lumps and tunnels can affect the rest of the body in ways that surprise many patients.
Joint pain is one of the more common non-skin symptoms. Studies have found that roughly 28% of people with HS also have spondyloarthritis, a type of inflammatory arthritis that primarily affects the spine and large joints. If you have HS along with persistent low back pain, swollen fingers, or stiff joints in the morning, those symptoms may be connected rather than coincidental.
The psychological burden is significant. People with HS report pronounced impacts on sexual function, work attendance, and social life. About 24% of HS patients carry at least one psychiatric diagnosis, a rate higher than what’s seen even in psoriasis, another chronic inflammatory skin condition. The risk of completed suicide is elevated in the HS population even after accounting for other risk factors. Feelings of stigmatization and isolation are common, driven by visible scarring, unpredictable drainage, and odor.
Fatigue is another frequent complaint, though it’s harder to pin down. Chronic inflammation taxes the body’s energy reserves, and the sleep disruption caused by pain during flares compounds the exhaustion.
Why HS Gets Misdiagnosed
That 10-year average diagnostic delay exists because early HS genuinely looks like other, more common conditions. A single painful lump in the armpit gets treated as a boil. Recurring groin lesions get labeled as ingrown hairs or folliculitis. Perianal abscesses may be attributed to Crohn’s disease or pilonidal cysts.
The pattern is what separates HS from these look-alikes. If you get painful lumps that keep returning in the same body folds, leave scars, or drain fluid, and especially if you notice the double blackhead formations, that recurring pattern is the clinical fingerprint of HS. Diagnosis is based on three criteria: typical lesions (nodules, abscesses, or sinus tracts), location in characteristic skin-fold areas, and a history of recurrence, generally defined as at least two flares over six months.