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Emergency Medicine > INFECTIOUS DISEASES
Cellulitis
Article Last Updated: Jul 8, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Danny Lee Curtis, MD, Consulting Staff, Department of Emergency Medicine, James A. Haley Veterans' Hospital, Tampa, FL; Assistant Professor of Medicine, University of South Florida, Tampa, FL
Danny Lee Curtis is a member of the following medical societies: American Academy of Emergency Medicine
Editors: Mark Louden, MD, FACEP, Assistant Medical Director, Emergency Department, Duke Raleigh Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Barry J Sheridan, DO, Chief, Department of Emergency Medical Services, Brooke Army Medical Center; John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center; Barry E Brenner, MD, PhD, FACEP, Program Director, Professor, Department of Emergency Medicine, Professor, Internal Medicine, University Hospitals, Case Western Reserve School of Medicine
Author and Editor Disclosure
Synonyms and related keywords:
cellulitis, inflammation of skin, skin infection, group A streptococci, Staphylococcus aureus, S aureus, group B streptococci, fungal cellulitis, erythema, Escherichiacolicellulitis, E coli cellulitis, gas gangrene, perianal cellulitis, facial cellulitis, lymphangitis
Background
The word cellulitis literally means inflammation of the cells. It generally indicates an acute spreading infection of the dermis and subcutaneous tissues resulting in pain, erythema, edema, and warmth.
For a related CME activity, see Managing the Complicated Skin and Soft Tissue Infection.
Pathophysiology
Skin and subcutaneous tissues are involved when microorganisms, typically gram-positive bacteria, invade disrupted skin. The infection triggers an inflammatory response that results in the clinically apparent pain, redness, warmth, and swelling.
Frequency
United States
Cellulitis is a common infection with an incidence of approximately 2-3 cases per 100 people per year.
It is more common in males and in those aged 45-64 years.
International
No geographic area is associated with the development of cellulitis.
Mortality/Morbidity
Cellulitis may progress to serious illness by uncontrolled spread contiguously or via the lymphatic or circulatory systems.
Race
No predilection exists.
Age
No predilection for age is known except as noted for facial cellulitis and perianal cellulitis.
- Facial cellulitis occurs more commonly in adults older than 50 years and in children aged 6 months to 3 years.
- Perianal cellulitis occurs predominantly in children. (This is somewhat of a misnomer, and the term perianal disease is preferred by some authors.)
History
The patient may have a history of trauma or surgery, causing a break in the skin, or may have no discernible dermal injury. The infection typically develops over a period of several days.
- Among those with peripheral vascular disease or diabetes, minor injuries or cracked skin in the feet or toes can serve as a source for infection.
- Foreign bodies passing through skin, such as intravenous catheters or orthopedic pins, can provide a portal of entry to infection.
- In those with prior surgery involving lymph node dissection, such as mastectomy, no evidence of recent injury may be observed. However, these patients are prone to recurrent cellulitis in these areas.
Physical
Hallmarks of cellulitis include the following:
- Warmth, erythema, edema, and tenderness of the affected area are present.
- Associated red streaking visible in the skin proximal to the area of cellulitis is characteristic of ascending lymphangitis. In lymphangitis, the infection is carried through the lymphatic system.
- Regional lymphadenopathy may be present.
- The margin of cellulitis will not be palpable.
- Fever may be present.
- Cellulitis characterized by violaceous color and bullae suggests infection with Streptococcus pneumoniae (pneumococcus).
Causes
- Bacterial and fungal infections
- In individuals with normal host defenses, the most common causative organisms are group A streptococci and Staphylococcus aureus.
- Cellulitis in infants may present as sepsis, most commonly caused by group B streptococci.
- In immunocompromised hosts, gram-negative rods or fungi may cause cellulitis, though fungal cellulitis is rare.
- Wounds occurring after exposure to fresh water may be caused by Aeromonas hydrophila, a gram-negative rod.
- Pneumococcus may cause a particularly malignant form of cellulitis, typically in an immunocompromised host, and frequently is associated with tissue necrosis, suppuration, and blood stream invasion.
- Patients with the following conditions are at increased risk of developing serious or rapidly spreading cellulitis:
- Diabetes
- Immunodeficiency
- Other systemic illness
- Varicella
- Impaired peripheral circulation (arterial insufficiency or venous stasis)
- Lymphadenectomy following tumor excision, such as mastectomy
- Postvenectomy status following saphenous vein stripping
- Chronic steroid use increases the risk of cellulitis.
- Cellulitis may complicate varicella.
- Cellulitis may be identified by a margin of erythema surrounding the vesicles.
- Although varicella is a viral illness and does not respond to antibiotics, the development of cellulitis complicating varicella mandates antibiotic treatment and careful clinical follow-up. Untreated cellulitis in association with varicella may progress to severe disfiguring gangrene of the dermal structures requiring skin grafting. Deaths have been reported.
Angioedema
Burns, Chemical
Dermatitis, Atopic
Dermatitis, Contact
Dermatitis, Exfoliative
Erysipelas
Erythema Multiforme
Gas Gangrene
Impetigo
Plant Poisoning, Toxicodendron
Stevens-Johnson Syndrome
Toxic Epidermal Necrolysis
Lab Studies
- No workup is required in uncomplicated cases that meet the following criteria:
- Small area of involvement
- Minimal pain
- No systemic signs of illness (eg, fever, chills, dehydration, altered mental status, tachypnea, tachycardia, hypotension)
- No risk factors for serious illness (eg, extremes of age, general debility, immunocompromise)
- Consider the following tests in more serious cases such as those in which systemic signs are present, those in which the patient is at high risk of complicated cellulitis, or when any of the risk factors listed in Causes are associated with the diagnosis.
- Complete blood count
- BUN level
- Creatinine level
- Blood cultures
- Aspiration of the wound
- Culture and Gram stain are of limited use.
- Yield is positive approximately one third of the time.
- Areas of abscess or bullae formation
- Culture and Gram stain of fluid may be helpful.
- Yield is positive approximately 90% of the time.
- Immunofluorescence: Direct immunofluorescence is technically possible and may lead to a definitive diagnosis in culture-negative cellulitis, but this is rarely necessary.
Imaging Studies
- Plain radiographs are unnecessary in uncomplicated cases.
- In more severe clinical cases, particularly with crepitus, radiographs may show gas in the tissues. If gas is seen, the differential diagnosis then includes fasciitis and gangrene, which generally are considered surgical emergencies.
Emergency Department Care
- Mild cellulitis
- Mild cellulitis may be treated on an outpatient basis with a regimen of oral antibiotics.
- Some clinicians prefer an initial dose of parenteral antibiotic with a long half-life, followed by an oral agent.
- Reevaluate within 24-48 hours. Patients who have not improved should be considered for admission.
- Complicated cellulitis: Patients with more extensive involvement, an underlying illness, or signs of systemic toxicity require admission to the hospital for intravenous antibiotics.
Consultations
- Patients with crepitus, extensive bullae formation, or necrosis of the skin require surgical consultation.
- Deep and rapidly spreading infections may develop into life-threatening emergencies. In such cases, patients require intensive monitoring, fluid and vasopressor support, broad-spectrum antibiotic coverage, and consideration for surgical debridement in the operating room.
The goals of therapy are to eradicate the infection and to prevent complications.
Drug Category: Antibiotics
Empiric coverage for group A streptococci and S aureus should be provided. Acceptable outpatient regimens include penicillinase-resistant synthetic penicillin or a first-generation cephalosporin. Alternatively, long-acting parenteral cephalosporin may be administered.
| Drug Name | Dicloxacillin (Dycill, Dynapen) |
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| Description | Bactericidal antibiotic that inhibits cell wall synthesis and is used to treat infections caused by penicillinase-producing staphylococci. May be used to initiate therapy when staphylococcal infection suspected. |
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| Adult Dose | 500 mg PO q6h |
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| Pediatric Dose | 50 mg/kg/d PO divided q6h |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Decreases efficacy of oral contraceptives; increases effects of anticoagulants; probenecid and disulfiram may increase levels |
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| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
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| Precautions | Monitor PT in patients taking anticoagulant medications; toxicity may increase in renal impairment |
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| Drug Name | Cephalexin (Keflex, Biocef) |
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| Description | First-generation cephalosporin that inhibits bacterial growth by inhibiting bacterial cell wall synthesis. Bactericidal and effective against rapidly growing organisms forming cell walls.
Primarily active against skin flora. Typically used for skin structure coverage and as prophylaxis in minor procedures. |
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| Adult Dose | 500 mg PO q6h |
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| Pediatric Dose | 50 mg/kg/d PO divided q6h |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Coadministration with aminoglycosides increases nephrotoxic potential; may increase toxicity of anticoagulants |
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| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
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| Precautions | Adjust dose in renal impairment because toxicity may increase; monitor PT in patients taking anticoagulant medications |
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| Drug Name | Ceftriaxone (Rocephin) |
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| Description | Third-generation cephalosporin that has broad-spectrum activity against gram-negative organisms, lower efficacy against gram-positive organisms, and higher efficacy against resistant organisms than earlier generation cephalosporins. By binding to 1 or more penicillin-binding proteins, arrests bacterial cell wall synthesis and inhibits bacterial growth. |
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| Adult Dose | 1-2 g IV/IM qd or divided bid, depending on type and severity of infection; not to exceed 4 g/d |
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| Pediatric Dose | Neonates >7 days: 25-50 mg/kg/d IV/IM divided bid; not to exceed 125 mg/d
Infants and children: 50-75 mg/kg/d IV/IM divided bid; not to exceed 2 g/d |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Probenecid may increase levels; coadministration with ethacrynic acid, furosemide, or aminoglycosides may increase nephrotoxicity |
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| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
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| Precautions | Adjust dose in renal impairment; caution in breastfeeding women and in those allergic to penicillin |
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| Drug Name | Nafcillin (Unipen) |
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| Description | Treats infections caused by penicillinase-producing staphylococci. Used to initiate therapy in patients who may have penicillin G-resistant staphylococcal infection. Do not use to treat penicillin G–susceptible staphylococcal infections.
Use parenteral therapy initially in severe infections. More severe infections may require very high doses. Change to oral therapy as condition improves.
Thrombophlebitis, associated with parenteral route, occurs occasionally, particularly in elderly persons. Thus, administer parenterally only for short term (24-48 h), and change to oral route if clinically possible. |
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| Adult Dose | 2 g IV/IM q4h |
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| Pediatric Dose | 150 mg/kg/d IV/IM divided q6h |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Associated with warfarin resistance when administered concurrently; bacteriostatic action of tetracycline derivatives may decrease effects |
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| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
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| Precautions | To optimize therapy, determine causative organisms and susceptibility; treat >10 d to eliminate infection and prevent sequelae (eg, endocarditis, rheumatic fever); take cultures after treatment to confirm that infection eradicated |
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| Drug Name | Cefazolin (Ancef, Kefzol, Zolicef) |
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| Description | First-generation semisynthetic cephalosporin that binds to 1 or more penicillin-binding proteins, arrests bacterial cell wall synthesis, and inhibits bacterial growth. Primarily active against skin flora, including S aureus. Typically used alone for skin and skin structure coverage.
Total daily dosages are same for IV and IM administrations. |
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| Adult Dose | 1 g IV/IM q8h |
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| Pediatric Dose | 20 mg/kg IV/IM q8h |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Probenecid prolongs effect; coadministration with aminoglycosides may increase renal toxicity; may yield false-positive urine-dip test result for glucose |
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| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
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| Precautions | Adjust dose in renal impairment; superinfections and promotion of nonsusceptible organisms may occur with prolonged use or repeated therapy |
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| Drug Name | Imipenem and cilastatin (Primaxin) |
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| Description | Used for severe disease. Used to treat multiple organism infections in which other agents do not have broad-spectrum coverage or are contraindicated because of their potential for toxicity. |
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| Adult Dose | 500 mg IV q6h |
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| Pediatric Dose | <12 years: Not established; 15-25 mg/kg/dose IV q6h; not to exceed 4 g/d suggested for >3 mo
>12 years: 50 mg/kg/d IV divided q6h; not to exceed 4 g/d |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Cyclosporine may increase adverse CNS effects of both agents; ganciclovir may result in generalized seizures |
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| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
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| Precautions | Adjust dose in renal insufficiency; avoid use in children <12 y when risks outweigh benefits |
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| Drug Name | Linezolid (Zyvox) |
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| Description | Prevents formation of functional 70S initiation complex, which is essential for bacterial translation process. Bacteriostatic against enterococci and staphylococci and bactericidal against most strains of streptococci. |
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| Adult Dose | 400-600 mg PO/IV q12h for 10-14 d |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity |
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| Interactions | May cause hypertension when used concomitantly with adrenergic agents, including pseudoepinephrine, sympathomimetic agents, and vasopressor or dopaminergic agents (reduce dose of dopamine or epinephrine if concurrent use required); serotonin syndrome may occur if used concomitantly with serotonergic agents, including tricyclic antidepressants, meperidine, dextromethorphan, trazodone, venlafaxine, and selective serotonin reuptake inhibitors |
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| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
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| Precautions | Has mild MAOI properties and has potential to have same interactions as other MAOIs; caution in uncontrolled hypertension, pheochromocytoma, carcinoid syndrome, or untreated hyperthyroidism, and in patients who are at increased risk for bleeding, have preexisting thrombocytopenia, receive concomitant medications that may decrease platelet count or function, or who may require >2 wk of therapy (monitor platelet counts); unnecessary use may lead to development of resistance to drug |
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| Drug Name | Ertapenem (Invanz) |
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| Description | Bactericidal activity results from inhibition of cell wall synthesis and is mediated through ertapenem binding to penicillin-binding proteins. Stable against hydrolysis by a variety of beta-lactamases including penicillinases, cephalosporinases, and extended-spectrum beta-lactamases. Hydrolyzed by metallo-beta-lactamases. |
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| Adult Dose | 1 g qd for 14 d if IV and 7 d if IM; infuse over 30 min if IV |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Probenecid may reduce renal clearance of ertapenem and increase half-life, but benefit is minimal and does not justify coadministration |
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| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
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| Precautions | Pseudomembranous colitis may occur; seizures and CNS adverse reactions may occur; when using with lidocaine to administer intramuscularly, avoid inadvertent injection into blood vessel |
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Further Inpatient Care
- Some patients may require admission for intravenous antibiotic therapy.
- Early discharge utilizing parenteral antibiotics on an outpatient basis has been shown to achieve cure of infection and improved patient satisfaction.
Further Outpatient Care
- Prophylaxis for recurrent cellulitis may be achieved by treatment with oral penicillin or erythromycin twice daily or intramuscular benzathine penicillin monthly.
Complications
- Bacteremia
- Local abscess
- Superinfection with gram-negative organisms
- Lymphangitis
- Thrombophlebitis
- Facial cellulitis in children - Causes meningitis in 8%
- Gas-forming cellulitis (gangrene) - May require amputation (25% mortality rate)
Prognosis
- The prognosis with uncomplicated cellulitis is good. Antibiotic regimens are effective in more than 90% of patients.
Patient Education
- Patients should be advised to seek medical care for worsening symptoms, including increasing pain, redness, and swelling; erythematous streaking proximal to the affected area; and fever and chills.
- For excellent patient education resources, see eMedicine's Diabetes Center. Also, visit eMedicine's patient education article Cellulitis.
Medical/Legal Pitfalls
- Failure to diagnose gas gangrene may have devastating consequences.
- Failure to admit patients with risk factors for developing severe cellulitis for intravenous antibiotic administration and observation may result in rapid disease progression.
Special Concerns
- Scar cellulitis is common in areas of previous burns, particularly those that required treatment with grafts.
- Escherichia coli cellulitis may develop in the presence of nephrotic syndrome.
- Cellulitis of the lower extremities is more likely to develop into thrombophlebitis in geriatric patients.
- Pseudomonads may cause cellulitis in immunocompromised children.
| Media file 1:
Severe cellulitis of the leg in a woman aged 80 years. The cellulitis developed beneath a cast and was painful and warm to the touch. Significant erythema is evident. Margins are irregular but not raised. An ulcerated area is visible in the center of the photograph. |
 |  View Full Size Image | |
Media type: Photo
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| Media file 2:
Severe cellulitis of the leg in a woman aged 80 years. This photograph shows intense erythema in a patchy distribution. An eroded area is visible near the center of the photograph. |
 | View Full Size Image | |
Media type: Photo
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| Media file 3:
Cellulitis complicating burns. Larger lesion is a second-degree burn and the smaller lesion is a first-degree burn, each with an expanding zone of erythema consistent with cellulitis. |
 | View Full Size Image | |
Media type: Photo
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| Media file 4:
Mild cellulitis with a fine lacelike pattern of erythema. This lesion was only slightly warm and caused minimal pain. This is typical for the initial presentation of mild cellulitis. |
 | View Full Size Image | |
Media type: Photo
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Cellulitis excerpt Article Last Updated: Jul 8, 2008
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