Cellulitis (Deep Skin Infection)

What is cellulitis?

Cellulitis is a condition of localized or diffuse skin infection by bacteria that extends into the deeper layers under the skin (subcutaneous tissue). The most common sites of infection include skin of the lower leg and face, although cellulitis can affect any parts of the body. Usually a break in the skin, even a minor abrasion, provides entry of infective bacteria into the body and deeper layers of tissue. Cellulitis can be effectively treated with antibiotics but if left untreated it can lead to life threatening complications like sepsis, shock and gangrene.

Cellulitis Symptoms

The skin has two layers – the outer epidermis and inner dermis. Underneath the dermis is the subcutaneous tissue, including the fatty layer that provides insulation and protection. Cellulitis extends as deep as the subcutaneous layer. Cellulitis presents with typical inflammatory changes of the infected skin like :

  • Redness
  • Pain and tenderness
  • Swelling with abscess (sometimes)
  • Warmth over the skin

The above mentioned symptoms can initially affect small areas of skin and progress rapidly to other areas. Other local symptoms may be temporary loss of hair over the affected skin, stretchy appearance of the skin and joint stiffness. Other associated symptoms are :

  • Fever may be with chill
  • Lethargy and weakness
  • Generalized body ache (malaise)
  • Profuse sweating
  • Nausea and vomiting
  • Swelling of local lymph nodes (glands)

Cellulitis often occurs simultaneously with another type of skin infection, erysipelas. Although erysipelas is a superficial infection not extending to the subcutaneous tissue, it can often be confused with cellulitis.

Causes of Cellulitis

Cellulitis, a bacterial infection, is most commonly caused by group A Streptococcus and Staphylococcus. These days infection with the more serious methicillin-resistant Staphylococcus aureus (MRSA) is becoming common. Sometimes the normally non-infective resident bacteria of the skin (skin flora) may lead to cellulitis in persons with poor immunity (immunocompromised).

The entry of bacteria occurs through break in the skin caused by cut, blister, ulcer, dermatitis, tattoo, insect (usually spider) biting, recent surgical wounds, puncture wounds, intravenous drug use in drug addicts or in patients with intravenous catheter. Upon entering the skin the bacteria rapidly spreads to other body parts via the blood stream and lymphatic spread. Under rare circumstances the bacteria (“flesh eating bacteria”) gain access to the deeper tissue (invading the fascial lining) causing necrotizing fasciitis.

One very specific form of cellulitis is Ludwig’s angina affecting the submandibular space (floor of the mouth). Dental infection (due to mixed bacterial infection) is the most common cause of Ludwig’s angina.

Risk factors

  • Advancing age – the elderly are at a greater risk.
  • Immunocompromised due to prolonged steroid use, chemotherapy, HIV patients.
  • Diabetics are a very high risk group.
  • Peripheral circulation disorders as there is poor blood supply to the legs in particular.
  • Chicken pox, shingles, eczema, athlete’s foot, superficial burn injury may cause breaks in the skin.
  • Swelling of legs – lymphedema, varicose veins.
  • Intravenous drug users
  • Prior history of cellulitis

Cellulitis Treatment

The standard treatment of cellulitis is oral or intravenous antibiotic therapy. Cellulitis is a very serious infection and patients on oral antibiotics need to use a course for at least 10 to 14 days. There is a high degree of recurrence if complete antibiotic therapy is not completed. In addition, topical antimicrobial agents may also be applied on open wounds to treat the superficial infection and prevent re-infection. Cellulitis is more common on the lower limb (leg) and patients should minimize movement during the early stages of treatment. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used to control pain and inflammation but antibiotic therapy is still essential. Surgical care may include :

  • Drainage of abscess
  • Debridement of necrotic tissue
  • Amputation in the event of gangrene of the limb

References :

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