What to Know About Hidradenitis Suppurativa Tunnels

In more advanced presentations, hidradenitis suppurativa (HS) can form “tunnels” or inflamed sinus tracts beneath the skin. These channels are frequently filled with pus or blood and can be quite painful.

Hidradenitis suppurativa (HS) usually presents as painful nodules, boils, and in some cases, subterranean tunnels.

Also referred to as fistulas, these sinus tracts most often develop in regions rich in sweat glands and where skin surfaces rub together, such as the armpits, groin, buttocks, or under and between the breasts.

While surface bumps and boils are often manageable with topical or oral therapies, the tunnels tend to be more refractory and sometimes necessitate surgical removal. Below is what to know about these lesions and available treatment options.

Why does HS produce tunnels?

Although researchers don’t fully understand  the exact cause or mechanism of hidradenitis suppurativa, it’s recognized as a chronic inflammatory disorder affecting hair follicles and sweat glands.

HS arises when hair follicles become blocked in areas prone to friction, driven by factors such as excess oil, accumulation of dead skin cells, and bacterial overgrowth. Many specialists believe these clogged follicles provoke an inflammatory reaction, which results in nodules and boils.

As inflammation escalates, these nodules and boils can evolve into tunnels beneath the skin because HS lesions may repeatedly rupture and then heal during flare-ups.

Notably, a 2022 study  suggested that the tunnels themselves may amplify the disease’s inflammation. Whereas they were once considered merely an outcome of inflammation, evidence now indicates they might actively perpetuate HS.

Consequently, clinicians believe that addressing only the visible rash isn’t sufficient; directly treating tunnels and the underlying inflammatory process, whether by surgical methods or medication, could be necessary to halt ongoing inflammation.

What do HS tunnels look like?

HS tunnels appear as  red or discolored, raised bands of skin. In people with darker complexions, they may look purple, dark brown, or gray. They typically arise in clusters in friction-prone regions like the armpits or buttocks and can range from a few centimeters to several inches long.

The sinus tracts are usually accompanied by other HS signs such as pustules and blisters. Over time, multiple tracts may form near one another and connect, increasing pain, irritation, and potentially causing lasting skin damage.

The tunnels are generally soft and tender and may be filled with pus or blood. They can have small openings that leak fluid, producing chronic drainage. Without treatment, these tracts often enlarge and lengthen over time, surrounded by markedly inflamed skin.

Eventually, they frequently lead to prominent rope-like scarring both within the tracts and on the adjacent skin.

Can you feel the tunnels from HS?

Many people with HS describe these tunnels as painful, with discomfort that intensifies as the tracts deepen, widen, and become more inflamed.

In earlier stages, tunnels may only be tender or mildly painful to touch. As they progress, many patients require prescription medications to control pain. Left untreated, the pain and disruption can substantially affect daily life.

Prior to a tunnel forming, you might notice a lump under the skin accompanied by some tenderness. This area can continue to swell and become more painful as a sinus tract develops.

How do you get rid of HS tunnels?

Although there’s no definitive cure for HS at present, several strategies can help manage it, including:

• Lifestyle adjustments: Clinicians commonly advise quitting smoking (if applicable) and achieving a healthy weight first. A 2019 study  identified regular smoking and higher body weight as major risk factors for recurrent tunnels.
• Medications: Tunnels may respond to saline injections, biologic agents, or corticosteroid injections. The 2022 study  reported that injections of the biologic brodalumab, which targets inflammatory pathways, led to marked shrinkage and reduced pus drainage.
• Surgery: Complete removal of tunnels often requires surgical treatment. In earlier tunnel formation, deroofing can be sufficient—this involves surgically removing the “roof” of the tract and cleaning out inflamed material to allow healing. In more extensive disease, full excision of the tracts may be necessary. After surgery, managing the underlying inflammation can help lower the chance of recurrence.

Ultimately, HS care must be tailored to each individual, so consult your healthcare provider to determine the best approach for you.

Healthline has also gathered a list of home and natural approaches that might help ease symptoms.

Takeaway

Untreated HS tunnels typically cause significant pain and can meaningfully reduce quality of life. Options such as saline injections, biologic therapies, and when needed, surgical removal, may be required to address the tracts.

Addressing underlying inflammation—by quitting smoking and maintaining a healthy weight—can help prevent recurrent tunnels. Because HS management is individualized, speak with a medical professional about the optimal treatment plan for your situation. For more information on related wound issues, see tunneling wound.