If you have hidradenitis suppurativa (HS), you might develop tunnels under your skin. These hollow pathways, called sinus tracts, can form between inflamed HS bumps. Over time, they may turn into scar tissue, which can make it harder to move that area, especially if the tunnels form near a joint.

In this article, we’ll discuss what HS tunnels are, why they form, and how your healthcare provider treats them. Call your dermatologist (skin specialist) when you notice new bumps, more pain, or other changes. Getting help early can stop tunnels from forming and help you feel better while living with HS.

Tunnel Formation in Hidradenitis Suppurativa

HS is an inflammatory skin condition that causes lumps or nodules to form underneath the skin. These nodules can look like acne, pimples, blackheads, or cysts (fluid-filled bumps). Sometimes, the lumps go away on their own.

Over time, HS nodules can grow and join together. They eventually form abscesses, which are painful lumps filled with pus (sometimes mixed with blood). They can also burst and leak fluid.

If left untreated, hollow tunnels can connect abscesses underneath the skin. The American Academy of Dermatology notes that tunnels form when abscesses repeatedly heal and reopen.

Research shows that having multiple HS tunnels is associated with:

• More severe disease activity
• Less response to medications, like biologics (medicines made in a lab from living cells)
• Severe pain
• Reduced quality of life

Symptoms of Hidradenitis Suppurativa Tunnels

One myHSteam member asked, “Does anyone get a bump or tunnel that never heals and just refills with fluid? It’s not really painful, but it’s irritating because it leaks when it wants without warning.”

“Does anyone get a bump or tunnel that never heals and just refills with fluid?”

— A myHSteam member

HS tunnels can fill with fluid, pus, or blood. If a tunnel connects to the surface of your skin, it may leak and give off an odor. Tunnels can also create scar tissue and leave permanent scars. Scar tissue isn’t as flexible as healthy skin. Thick scars can become severe enough that they limit your range of motion (how far you can freely move).

Where Do Hidradenitis Suppurativa Tunnels Develop?

In HS, your immune system mistakenly attacks your hair follicles, which are tiny pockets in the skin where hair grows. This produces inflammation that leads to nodules and abscesses. Tunnels can develop anywhere you have these lumps.

HS tends to affect areas of skin where you have more hair follicles or where your skin rubs together. Here are places where HS tunnels may form:

• Armpits
• Breasts or the area below
• Waist or lower part of the abdomen
• Inner thighs
• Groin area
• Genitals
• Buttocks
• Area of skin between the genitals and anus

Tunnels can also cover large areas of skin and connect multiple lumps. One myHSteam member shared, “I’m afraid that my tunnels are now spreading from just below my butt to my inner thighs. I’ve been dressing them, but the sores on my inner thighs are oozing a lot.”

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Research shows that HS tunnels can form in the skin and the tissue underneath it. These layers each do different jobs:

• Epidermis (top) — Makes new skin cells
• Dermis (middle) — Contains hair follicles, blood vessels, and nerves
• Hypodermis (bottom) — Provides cushioning connective tissue around bones and muscles

Treatments for Hidradenitis Suppurativa Tunnels

Doctors use a combination of surgery and medications to treat HS tunnels. A few types of surgery can be used to treat HS and tunnels. Your dermatologist or surgeon will choose the procedure based on where the tunnels are and how severe your symptoms are.

One myHSteam member shared their experience with surgery. “Just had surgery under my arm to remove the sinus tract last week,” they said. “That was the last bump from HS. I’ve been doing so well — no breakouts at all.”

“Just had surgery under my arm to remove the sinus tract last week. I’ve been doing so well — no breakouts at all.”

— A myHSteam member

Doctors can also use medications to treat inflammation and clear up nodules and abscesses. This treatment may stop tunnels from forming under the skin.

Deroofing

Deroofing is typically used in the first two stages of HS. During this procedure, the surgeon removes the “roof,” or skin on top of the tunnel, and scrapes out the tissue inside the tunnel. The healthy cells from the hair follicles and sweat glands heal the wound.

A myHSteam member described their experience with deroofing surgery: “My surgeries consisted of slicing open the top of the nodule, scraping out the infection and tunnels, and laying skin back over the wound.” Studies show that deroofing is generally successful and often lowers the chance that lesions return.

Incision and Drainage

To relieve HS symptoms, doctors may suggest incision and drainage. The doctor numbs the affected area and makes an incision (small cut) in the abscess, then drains fluid or pus.

The relief from incision and drainage is usually temporary. Your abscesses will probably return, so this procedure isn’t used as often.

Wide Excision

If your HS tunnels can’t be treated with other surgeries or medications, your dermatologist may recommend a wide excision. This procedure removes the entire tunnel with the fat or skin around it. Before surgery, your surgeon may use imaging tests, such as an ultrasound or MRI, to see where the tunnels are and how far they spread.

Surgeons usually leave a wide excision wound open to heal on its own. In some cases, you may need another surgery to replace the removed tissue. Your surgeon can use some of your own healthy skin to make a skin graft to cover the wound. This graft helps it heal properly.

Biologics

Doctors also use medications called biologics to treat HS. They work by lowering inflammation. Biologics are usually used to treat moderate to severe HS. These injected medications help reduce HS symptoms like nodules, abscesses, and tunnels.

Preventing Hidradenitis Suppurativa Tunnels

Early treatment of HS may prevent tunnels from forming. Your dermatologist can help you explore treatment options that reduce inflammation and prevent flare-ups. Your healthcare provider may prescribe these medications to treat HS:

• Antibiotics
• Oral retinoids
• Hormonal medications

The Bottom Line

Getting care early can make a big difference. Treatment with medicine, surgery, or both can help stop tunnels from getting worse and lower the chance of new ones forming. Following your treatment plan can also help prevent new bumps and abscesses, which may mean less pain and fewer flare-ups over time.

Join the Conversation

On myHSteam, people share their experiences with hidradenitis suppurativa, get advice, and find support from others who understand.

Do you have tunnels with your HS? Let others know in the comments below.