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Symptoms – Infection

Doctors once believed that bacterial infection caused hidradenitis suppurativa (HS). However, research now shows that this is not the case.1,2

HS is a painful, chronic inflammatory skin disease. The disease begins when clogged hair follicles cause bumps. Over time, the process causes:2

  • Abscesses
  • Pus
  • Odor
  • Inflammation
  • Tunnels under the skin
  • Scars

Flares that come and go also make HS symptoms worse.3

What causes HS?

Research has not found an exact cause for HS. Doctors think several factors play a part, including:2,4

  • Genetics
  • Environment
  • Hormones
  • Microbiology

Doctors now seem to agree that infection is not likely to be the primary cause of HS.2,4

A current theory is that a genetic defect causes overproduction of keratin, a tough protein that forms hairs and nails. The keratin plugs hair follicles, which are tiny canals in the skin where hairs grow. Bumps and lesions (sores) result.1

Researchers have not found harmful bacteria in HS lesions. They have found only normal microorganisms that do not cause disease. One theory is that an overactive immune system in people with HS causes an extreme inflammatory response to harmless microorganisms.1,2

However, researchers found that the balance of microorganisms in the skin of people with HS is different from the skin of people without the condition. They believe that in people with HS, bacteria may build biofilms. Biofilms are colonies of bacteria that stick to each other and to other surfaces, such as hair follicles and tunnels under the skin.5

What do infections do?

Biofilm infections cause chronic inflammation and worsen the disease. They lead to larger lesions and more pus. It is hard to get rid bacteria in biofilms, and this may explain why antibiotics take a long time to work against HS.1,2

Infections may have more roles in HS, including:4-7

  • Bacteria infect plugged hair follicles and produce odor and pus. The lesions and follicles burst and spill their contents into the surrounding dermis, the thickest layer of skin. This causes more inflammation and more bumps. The process repeats.
  • Cellulitis is possible but not common. Cellulitis is a spreading, bacterial skin infection. It causes redness, warmth, swelling, and pain. Cellulitis requires antibiotic treatment.
  • Septicemia is extremely rare as a complication of HS. Septicemia is a serious, sometimes fatal, infection in the bloodstream. Treatment requires antibiotics and hospitalization.

Sometimes infections occur as side effects of HS treatments, including:4,8-10

  • By killing off the “good” bacteria (microorganisms that protect the skin), antibiotics may allow the growth of yeast and harmful bacteria that resist antibiotics.
  • Treatment with TNFα blockers (drugs that help stop inflammation) to reduce HS inflammation also decreases immune function. It may lead to viral infections, such as herpes and shingles.
  • Allowing wide surgical wounds to heal slowly without closing the sides exposes them to infection.

More research for better treatment

Treatment of HS is complex, and infection is just 1 part of the condition that needs to be managed. More research is needed to help doctors guide and develop better treatments for people with HS.

Written by: Ina Fried | Last reviewed: December 2020
  1. Constantinou CA, Fragoulis GE, Nikiphorou E. Hidradenitis suppurativa: infection, autoimmunity, or both? Ther Adv Musculoskel Dis. 2019 Dec 30;11:1-14. doi:10.1177/1759720X19895488.
  2. Seyed Jafari SM, Hunger RE, Schlapbach C. Hidradenitis suppurativa: current understanding of pathogenic mechanisms and suggestion for treatment algorithm. Front Med (Lausanne). 2020 Mar 4;7:68. doi:10.3389/fmed.2020.00068.
  3. Jemec GBE. Clinical practice: Hidradenitis suppurativa. N Engl J Med. 2012 Jan 12;366(2):158e64. Available at Accessed 7/12/2020.
  4. Margesson LJ, Danby FW. Hidradenitis suppurativa. Best Pract Res Clin Obstet Gynaecol. 2014 Oct;28:1013-1027.
  5. Dermatology glossary of terms. DermNet NZ. Available at Accessed 7/17/2020.
  6. Slade DEM, Powell BW, Mortimer PS. Hidradenitis suppurativa: pathogenesis and management. British Association of Plastic Surgeons. 2003;56:451-461.
  7. Maitre S. Cellulitis: definition, etiology, diagnosis and treatment. Virtual Mentor. 2006;8(12):831-833. doi:10.1001/virtualmentor.2006.8.12.cprl1-0612.
  8. Devillers C, Piérard-Franchimont C, Piérard GE. Comment je traite ... une hidradénite suppurée. Rev Med Liège 2009; 64:2:63-65. Available at Accessed 7/16/2020.
  9. Information on tumor necrosis factor (TNF) blockers (marketed as Remicade, Enbrel, Humira, Cimzia, and Simponi). U.S. Food and Drug Administration. Available at Accessed 7/21/2020.
  10. Alikhan A, Sayed C, Alavi A, et al. North American clinical management guidelines for hidradenitis suppurativa: a publication from the United States and Canadian Hidradenitis Suppurativa Foundations: Part I: Diagnosis, evaluation, and the use of complementary and procedural management. J Am Acad Dermatol. 2019;81(1):76‐90.