Cellulitis is a diffuse inflammatory condition of the skin and subcutaneous tissues. It characteristically presents with localized pain and tenderness, edema, erythema, and heat. Cellulitis occurs most often in the lower extremities, but it may also occur in the upper extremities as well as the face and scalp. It is most often caused by pathogens of the skin such as group A streptococci (Streptococcus pyogenes) and Staphylococcus aureus; however, other causative organisms are groups B, C, and G streptococci, Haemophilus influenzae (periorbital cellulitis in children), Pseudomonas aeruginosa (cellulitis in immunocompromised hosts), as well as atypical gram-negative bacteria and cryptococci. S. pyogenes is the most common cause of erysipelas, a superficial cellulitis seen most often on the face and scalp; Erysipelothrix rhusiopathiae is the causative organism of cellulitis among fish and meat handlers; and Mycobacterium marinum causes cellulitis among patients exposed to water in aquariums and swimming pools. Erysipelas is a type of superficial cellulitis (most commonly seen in infants, young children, and elderly), which includes lymphatic involvement and is almost invariably due to group A streptococci (less commonly, group C or G).

A history of a preceding injury to the skin such as cuts, insect bites, trauma, burns, surgical incisions, intravenous catheters, or an underlying disorder such as stasis dermatitis or psoriasis account often precede the development of cellulitis. A systemic infection may spread to the skin and subcutaneous tissue; although rare with cellulitis, an upper respiratory infection precedes erysipelas in one-third of the patients with this latter condition. Occasionally, there is no obvious inciting event for either cellulitis or erysipelas.

• Cachexia 
• Diabetes 
• Peripheral vascular disease 
• Malnutrition 
• Contaminated wounds 
• Immunosuppression 
• Systemic infections 
• Sinusitis, otitis media, or epiglottitis may precede periorbital cellulitis, especially in children 
• Lymphedema from pelvic surgery, radiation therapy, or lymph node metastases 
• Bites of cats and dogs or other animals – causing infection by Pasturella and a variety of anaerobic organisms 
• Venous surgery 

Local symptoms:

• Pain and tenderness 
• Edema 
• Erythema, which blanches on palpation 
• Heat 
• Indistinct borders 
• Crepitus or bullae formation in the soft tissue may be indicative of bacteremia 

Systemic symptoms:

• Malaise 
• Fever 
• Chills 
• Hypotension or confusion may occur in the case of sepsis 

• Herpes zoster 
• Insect bites 
• Contact dermatitis 
• Chemical or thermal burns 
• Deep vein thrombosis (DVT) 
• Giant urticaria 
• Lymphatic cutaneous metastases 
• Diffuse inflammatory breast carcinoma may mimic erysipelas in that location 
• Also want to be aware of the possibility of septic or inflammatory joints, abscess formation, necrotizing fasciitis, and gangrene (see section entitled Complications/Sequelae) 

A thorough physical examination is performed to determine the portal of entry of the pathogen. Antimicrobial therapy should not be delayed until laboratory results are in hand because cellulitis may rapidly progress to a serious systemic infection. Suspicion of gangrene or abscess warrants surgical consult and evaluation.

Diagnostic tests are used to try to identify the causative organism; however, the results are often inconsistent and therefore disappointing, isolating the pathogen in only 10% to 50% of cases. Thus, the diagnosis is usually made clinically.

• Gram's stain and culture from an open wound and/or obvious portal of entry 
• Punch biopsy of the lesions 
• Fine-needle aspiration of the advancing edge of the cellulitis
• Blood cultures if suspected bacteremia 
• WBC count may reveal leukocytosis, common with erysipelas 

• X rays may show air in tissues or periosteal inflammation 
• Computed tomography scan, to diagnose orbital cellulitis 
• Bone scan if underlying osteomyelitis is suspected 
• Doppler studies may be ordered to assess for DVT 

• Immunofluorescence 
• Latex agglutination 
• Ankle-brachial indices, pulse volume recordings, and arteriogram if vascular disease is suspected 

Although treatment with antibiotics usually brings rapid relief, patients should also maintain complete bed rest, immobilization and elevation of the affected extremity, and cool, wet, sterile, saline dressings for local relief.

Antibiotics are the mainstay of therapy. Analgesics for pain may also be useful.

Mild cellulitis:

• For streptococcal origin: aqueous penicillin G (600,000 units) injection followed by intramuscular procaine penicillin (600,000 units every 8 to 12 hours). Alternatives may be needed for penicillin-resistant strains of bacteria. 
• For staphylococcal origin: dicloxacillin, 0.25 to 0.5 g orally every six hours 
• For penicillin-allergic adults: erythromycin, 0.5 g orally every six hours 

Cellulitis in high-risk patients and/or if systemic infection or complications present or suspected, hospital observation warranted:

• For staphylococcal or streptococcal origin: nafcillin, 1.0 to 2.0 g intravenously every four hours or cefazolin 1.0 g IV q 8 hours 
• For penicillin-allergic adults: vancomycin, 1.0 to 1.5 g/day intravenously (facial erysipelas); erythromycin or azithromycin for cellulitis 
• For gram-negative bacilli: an aminoglycoside such as gentamicin
• For diabetic patients: parenteral cefazolin or cefoxitin plus gentamicin, or clindamycin and gentamicin 

If antibiotics fail to produce a prompt clinical response, surgery may be necessary to drain any underlying abscess.

Cellulitis can progress rapidly and, as stated earlier, antibiotic therapy is recommended to prevent systemic bacteremia. Most CAM therapies have not yet been scientifically evaluated for use in cellulitis.

According to the results of one case study, though, magnet therapy may help heal chronic wounds. The patient was a woman with a history of cellulitis originating at the site of an abdominal scar. Conventional treatments such as antibiotic therapies, antifungal medications, and wet-to-dry dressings were used over the course of a year but failed to heal this persistent wound. There were no obvious medical complications retarding wound healing. A permanent magnet, 650 gauss in strength, was placed on top of a gauze dressing and secured with tape. No other changes were made in a dressing protocol of antibiotic ointment covered with gauze and changed twice daily. The magnet was worn at all times except when the dressing was being changed. On her first return visit 11 days after the application of the magnet, the wound was considerably smaller in size. The following week, there was no change in size but the reddened scar tissue was lighter in color and smoother in texture. By the last visit, 4 weeks after beginning magnet therapy, the wound had completely healed (Szor and Topp 1998).

There are many theories about how magnet therapy works to reduce pain and inflammation; however, none are definitive. Theories include: increased circulation to the affected area, with removal of metabolic waste products and delivery of nutrients; pain relief due to neural stimulation; changes in cellular conductivity caused by realignment of molecules in cell membranes; influence on the pineal gland, resulting in altered production of melatonin, serotonin, and various enzymes; and decreased levels of cholinesterase, or inhibition of its accumulation, thereby altering metabolism of neurotransmitters at the synapse (Szor and Topp 1998). It will be interesting to see if future research replicates these results.

Specific nutrients have not been studied in relationship to cellulitis. However, vitamins known to be supportive of the immune system include vitamin C, zinc, and vitamins A and E. The latter two are also thought to have specific benefit for the skin (Keller and Fenske 1998). In addition, flavonoids appear to be useful in reducing swelling for lymphedema and may also be helpful in treating swelling associated with cellulitis (Mortimer 1997). There is, however, no known scientific literature confirming the effectiveness of this latter application. Bromelain may also be used clinically to reduce inflammation and edema (250 to 500 mg tid); it works well in combination with quercetin, a flavonoid. Please see corresponding monographs on each of these topics for additional information.

Although there are no studies validating their use for cellulitis specifically, herbs that provide immune support may be beneficial. Echinacea (Echinacea spp.) is widely used in clinical practice for immunomodulation in the case of an infection; yarrow (Achillea millefolium) is used for similar purposes. Comfrey root (Symphytum officinale) is an anti-inflammatory from which a paste can be made and applied topically bid to speed healing and minimize superinfection (Blumenthal et al. 2000). Goldenseal root (Hydrastis canadensis) and slippery elm (Ulmus fulva) may be added to a topical comfrey paste for enhanced therapeutic benefit.

Homeopathic treatment can address both constitutional and acute aspects of disease in general. In homeopathic terminology, the constitutional state reflects a pattern of underlying vulnerability or weakness that is unique to the individual and persists throughout that person's life. Symptoms tend to alternate over time, and treatment consists of selecting the appropriate remedy specific for the patient's constitutional type. By contrast, in acute conditions, such as cellulitis, a remedy may be administered without reference to any particular constitutional state (Ullman 1995).

Morrison describes several homeopathic remedies for use in erysipelas: Apis, Borax, Cantharis, Crotalus horridus, Graphites, Lachesis, Mercurius, Rhus toxicodendron, and Sulphur (Morrison 1993). French and Belgian homeopaths have been treating cellulitis clinically with homeopathic remedies since the 1960s. It is best to consult a licensed, certified homeopath to treat an individual most appropriately.

Acupuncture and other traditional Chinese medicine practices may be helpful in addressing the underlying etiology and enhancing immune function; however, this application in the treatment of cellulitis has not been investigated.

Massage is contraindicated in cases of active infection. However, when used to promote lymphatic drainage, as in the case of stasis or lymphedema, massage together with compression and exercise may be a useful prophylactic treatment in the case of recurrent cellulitis secondary to these etiologies (Mortimer 1997).

Cellulitis should be treated as a dermatologic emergency, and all patients should be carefully followed. Otherwise, serious complications such as gangrene could result.

Secondary bacterial infections are not uncommon. All patients must be monitored to be sure that the cellulitis resolves satisfactorily. Immunocompromised patients will need more aggressive attention.

Complications of cellulitis are uncommon but are most often seen in very young children, the elderly, or in immunocompromised patients.

• Gangrene 
• Metastatic abscess 
• Sepsis 
• Thrombophlebitis (predominantly in lower extremities of the elderly) 
• Lymphadenitis 

Although antibiotic therapy most often cures the cellulitis, death from complications may occur. A thorough history is important as some patients tend to develop recurrent cellulitis, often in the same area, leading to permanent changes. Long-term neglect and poor skin hygiene may result in a rare condition, elephantiasis nostras, which is characterized by thickened skin and verrucous lesions resembling crowded wart-like growths.

Patients on a maternity ward who develop cellulitis should be temporarily isolated as a precaution.

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