Skin and soft tissue infections

Last updated: November 1, 2023

Summarytoggle arrow icon

Skin and soft tissue infections (SSTIs) are a group of heterogeneous conditions affecting the epidermis, dermis, subcutaneous tissue, or superficial fascia. Uncomplicated infections are most commonly caused by gram-positive pathogens (Streptococcus, Staphylococcus) that infiltrate the skin after minor injuries (e.g., scratches, insect bites). Complicated infections have a higher tendency to be polymicrobial. SSTIs primarily manifest with painful, warm, erythematous skin lesions and may also lead to purulent fluid collections and/or necrosis of the affected tissue. Systemic symptoms like fever are usually a sign of more severe infections. Risk factors for developing SSTIs (or more severe forms of SSTIs) include diabetes mellitus, immunodeficiency, and chronic edema. Diagnosis is mostly clinical but some patients may require imaging or laboratory studies. Purulent infections, such as abscesses, are primarily treated with incision and drainage while nonpurulent infections (e.g., erysipelas, cellulitis) require antibiotic therapy. Necrotizing soft tissue infections (NSTIs) have a high mortality rate; they are a surgical emergency and require immediate wound debridement.

Overviewtoggle arrow icon

Overview of skin and soft tissue infections
Condition Most common pathogens Tissue involvement Clinical features

Staphylococcal scalded skin syndrome (generalized form of impetigo)

Nonpurulent SSTIs Erysipelas
Purulent SSTIs Skin abscess
  • Deeper layers of the skin
  • Walled-off infection with a collection of pus
Folliculitis, furuncles, carbuncles
Necrotizing soft tissue infections
  • Severe, rapidly progressive infection with necrosis
  • Possible crepitus, bullae, and purple skin discoloration
  • High risk of systemic complications, high mortality

Tissue involvement of SSTI (from superficial to deep): impetigo (superficial epidermis), erysipelas (superficial dermis and lymphatic vessels), cellulitis (deep dermis and subcutaneous tissue), necrotizing fasciitis (subcutaneous tissue including superficial and deep fascia)

Cardinal signs of inflammation

Risk factors for skin and soft tissue infections [1]


  • Local spread of infection
  • Systemic involvement with fever and possible sepsis (see “Sepsis” for details on the management of severe infections)
  • Spread of infection to distant sites (see “Staphylococcal infections”)


Nonpurulent skin and soft tissue infectionstoggle arrow icon

Definitions [3][4]

Clinical features [3][4]

Bilateral cellulitis is exceedingly rare. Patients presenting with bilateral leg erythema should also be evaluated for alternative diagnoses, including stasis dermatitis and lymphedema. [5]

Pathophysiology [3][4]

  • Entry is commonly via a minor skin injury ; erysipelas can consequently spread via superficial lymphatic vessels.
  • May also be secondary to a systemic infection

In both erysipelas and cellulitis, the most common point of entry for the pathogen is a small skin lesion (e.g., interdigital tinea pedis).

Etiology [3][4]

GAS is the most common cause of nonpurulent skin and soft tissue infections (i.e., erysipelas, cellulitis).

Diagnostics [3][6]

Diagnosis is usually clinical. In patients with systemic symptoms, laboratory studies, cultures, and imaging may be indicated to assess severity and tailor treatment.

Treatment of nonpurulent SSTIs [1][3][8]

General principles

Antibiotic therapy

Antibiotics should be targeted against gram-positive pathogens and provide broad-spectrum coverage in severe cases. [4]

Supportive care

Acute management checklist for nonpurulent SSTI

Subtypes and variants

Perianal streptococcal dermatitis


Complications [3][4]

Purulent skin and soft tissue infectionstoggle arrow icon

Folliculitis, furuncles, and carbuncles [3]

Facial furuncles can result in severe complications (e.g., periorbital cellulitis, cavernous sinus thrombosis).

Skin abscess [3][4]

In both scrotal abscess and epididymitis, the classic signs of inflammation are prominent and help to confirm the diagnosis.

Etiology [3]

Diagnostics [1][3]

Diagnosis is usually clinical. In patients with systemic symptoms, laboratory studies, cultures, and imaging may be indicated to assess severity and tailor treatment.

Treatment of purulent SSTIs

General principles

  • Incision and drainage are the mainstay of treatment for purulent SSTIs and are usually sufficient for mild infections.
  • Patients with systemic signs of infections require empiric antibiotic therapy.
  • Outpatient management is appropriate for clinically stable patients.
  • Consider inpatient management for patients with systemic symptoms.
  • See “Sepsis” for more details on the management of severe infections.

Interventional therapy [3][4]

Antibiotic therapy [3][4]

Mild purulent skin infections usually do not require systemic antibiotic treatment following drainage.

Supportive measures

Acute management checklist for moderate and severe purulent infections

Necrotizing soft tissue infectionstoggle arrow icon

Definitions [3][4]

Etiology [3][4]

The only way to definitively establish the causative pathogen is by obtaining a deep tissue culture (i.e., during surgical exploration). Clinical features alone are not reliable enough to distinguish between pathogens.

Clinical features [3][4]

Necrotizing fasciitis first spreads along the fascia before spreading to the superficial cutaneous tissue. Local findings may, therefore, be unremarkable, with patients experiencing a disproportionate level of pain.

Red flags that suggest necrotizing deep tissue infection include the presence of crepitus, bullous lesions, skin necrosis, pain out of proportion to examination, and signs of systemic toxicity (especially altered mental status).

Diagnostics [3]

A definitive diagnosis is usually made during the visualization of the tissue during surgery.

Do not delay surgical consultation and definitive surgical intervention for imaging and laboratory studies.

Superficial wound cultures may not accurately represent the pathogens found in deep tissue and should not be used to guide management.

Management [3][4]

Necrotizing soft tissue infections are a surgical emergency. Expedite and prioritize surgical exploration for diagnostic confirmation and debridement as much as possible!

Surgical exploration and debridement

  • Procedure [4]
    • Extensive exploration with surgical debridement (removal of necrotic tissue)
    • Obtain deep tissue samples for Gram stain, cultures, and histopathology.
    • Tissue with uncertain perfusion may be left for reassessment on a second intervention.
    • Reexploration every 12–36 hours until there is no evidence of necrotic tissue
  • Supportive findings
    • Fascia appears swollen
    • Dull gray fascia; areas of necrosis may be visible
    • Possible brown exudate (no pus)
    • Easy dissection of tissue planes with a blunt instrument or gloved finger

Antibiotic therapy [3][4]

Acute management checklist for necrotizing SSTI


Differential diagnoses

Antibiotic therapy for skin and soft tissue infectionstoggle arrow icon

Severity of SSTI [3]

SSTI severity grading [3]
Grade Characteristics


  • Locally confined
Moderate SSTI
  • Systemic symptoms
Severe SSTI

Necrotizing infections are always considered severe!

Empiric antibiotic therapy [3]

Empiric antibiotic therapy for skin and soft tissue infections (based on the 2014 IDSA guidelines) [1][3][4]

Mild infection

Moderate infection

Severe infection

Purulent SSTI

Nonpurulent SSTI

Necrotizing SSTI

  • Necrotizing infections are always considered severe.

Differential diagnosestoggle arrow icon

Ecthyma gangrenosum



The differential diagnoses listed here are not exhaustive.

Referencestoggle arrow icon

  1. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014; 59 (2): p.e10-52.doi: 10.1093/cid/ciu444 . | Open in Read by QxMD
  2. Sartelli M, Guirao X, Hardcastle TC, et al. 2018 WSES/SIS-E consensus conference: recommendations for the management of skin and soft-tissue infections. World Journal of Emergency Surgery. 2018; 13 (1).doi: 10.1186/s13017-018-0219-9 . | Open in Read by QxMD
  3. Brook I, Frazier EH. Clinical and microbiological features of necrotizing fasciitis.. J Clin Microbiol. 1995; 33 (9): p.2382-7.doi: 10.1128/JCM.33.9.2382-2387.1995 . | Open in Read by QxMD
  4. Expert Panel on Musculoskeletal Imaging:., Beaman FD, von Herrmann PF, et al. ACR Appropriateness Criteria® Suspected Osteomyelitis, Septic Arthritis, or Soft Tissue Infection (Excluding Spine and Diabetic Foot). J Am Coll Radiol. 2017; 14 (5S): p.S326-S337.doi: 10.1016/j.jacr.2017.02.008 . | Open in Read by QxMD
  5. Jameson JL, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J. Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2). McGraw-Hill Education / Medical ; 2018
  6. Walls R, Hockberger R, Gausche-Hill M. Rosen's Emergency Medicine. Elsevier Health Sciences ; 2018
  7. Raff AB, Kroshinsky D. Cellulitis. JAMA. 2016; 316 (3): p.325.doi: 10.1001/jama.2016.8825 . | Open in Read by QxMD
  8. Ramakrishnan K, Salinas RC, Agudelo Higuita NI. Skin and Soft Tissue Infections. Am Fam Physician. 2015; 92 (6): p.474-83.
  9. Chitalia VC, Kothari J, Wells EJ, et al. Cost-benefit analysis and prediction of 24-hour proteinuria from the spot urine protein-creatinine ratio.. Clin Nephrol. 2001; 55 (6): p.436-47.
  10. Miller LG, Quan C, Shay A, et al. A Prospective Investigation of Outcomes after Hospital Discharge for Endemic, Community-Acquired Methicillin-Resistant and -Susceptible Staphylococcus aureus Skin Infection. Clinical Infectious Diseases. 2007; 44 (4): p.483-492.doi: 10.1086/511041 . | Open in Read by QxMD
  11. Klevens RM, Morrison MA, Nadle J, et al. Invasive methicillin-resistant Staphylococcus aureus infections in the United States.. JAMA. 2007; 298 (15): p.1763-71.doi: 10.1001/jama.298.15.1763 . | Open in Read by QxMD
  12. Summanen PH, Talan DA, Strong C, et al. Bacteriology of Skin and Soft-Tissue Infections: Comparison of Infections in Intravenous Drug Users and Individuals with No History of Intravenous Drug Use. Clinical Infectious Diseases. 1995; 20 (Supplement_2): p.S279-S282.doi: 10.1093/clinids/20.supplement_2.s279 . | Open in Read by QxMD
  13. Talan DA, Moran GJ, Krishnadasan A, et al. Subgroup Analysis of Antibiotic Treatment for Skin Abscesses. Ann Emerg Med. 2018; 71 (1): p.21-30.doi: 10.1016/j.annemergmed.2017.07.483 . | Open in Read by QxMD
  14. Daum RS, Miller LG, Immergluck L, et al. A Placebo-Controlled Trial of Antibiotics for Smaller Skin Abscesses. N Engl J Med. 2017; 376 (26): p.2545-2555.doi: 10.1056/nejmoa1607033 . | Open in Read by QxMD
  15. Gottlieb M, DeMott JM, Hallock M, Peksa GD. Systemic Antibiotics for the Treatment of Skin and Soft Tissue Abscesses: A Systematic Review and Meta-Analysis. Ann Emerg Med. 2019; 73 (1): p.8-16.doi: 10.1016/j.annemergmed.2018.02.011 . | Open in Read by QxMD
  16. Duane TM, Huston JM, Collom M, et al. Surgical Infection Society 2020 Updated Guidelines on the Management of Complicated Skin and Soft Tissue Infections. Surg Infect (Larchmt). 2021; 22 (4): p.383-399.doi: 10.1089/sur.2020.436 . | Open in Read by QxMD
  17. Liu C, Bayer A, Cosgrove SE et al. Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children. Clin Infect Dis. 2011; 52 (3): p.e18-55.doi: 10.1093/cid/ciq146 . | Open in Read by QxMD
  18. Mermel LA, Allon M, Bouza E, et al. Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2009; 49 (1): p.1-45.doi: 10.1086/599376 . | Open in Read by QxMD
  19. Fitch MT, Manthey DE, McGinnis HD, Nicks BA, Pariyadath M. Abscess Incision and Drainage. N Engl J Med. 2007; 357 (19): p.e20.doi: 10.1056/nejmvcm071319 . | Open in Read by QxMD

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