Cellulitis (Skin Infection) Treatment

What is Cellulitis?

Cellulitis is the medical term for infection of the skin.  It typically occurs when there is an opening in the skin such as a laceration or abrasion allowing bacteria to enter and proliferate in skin tissue.  Patients classically develop spreading redness, warmth, swelling, and pain in the involved region.  They also often have a fever.  Some skin infections spread rapidly and invade the surrounding soft tissue and fascia.  This may be life threatening and typically occurs due to infection with “flesh-eating” bacteria – a condition termed necrotizing fasciitis.

Due to the importance of this condition, it is critical that patients understand its causes, symptoms, and treatment.  By the end of this article, you will have the answers to these essential questions

What causes Cellulitis?

Cellulitis is caused by bacterial infection of the skin.  The microorganisms are usually of the gram positive variety such as staphylococcus and streptococcus species.  These bacteria normally colonize our skin without causing infection; however, bacteria can enter the tissue when there is an opening in the skin (e.g., cut, scrape).  The bacteria can then proliferate in the wound and spread into the surrounding skin. This causes the cardinal signs of inflammation – warmth (calor), redness (rubor), pain (dolor), and swelling (tumor).

Sometimes, aggressive strains of bacteria such as methicillin resistant S. aureus (MRSA) infect skin tissue, which often results in the formation of boils or abscesses.  These are pockets in the skin and soft tissue that contain pus, dead tissue, and bacteria.  Occasionally, bacteria such as Clostridium perfringens or Pseudomonas will be responsible for skin and soft tissue infection especially in frequently hospitalized patients and those with diabetes mellitus.

Severe cases of cellulitis can be associated with gas gangrene and tissue necrosis – death of skin tissue.  These cases often require intravenous antimicrobial therapy and surgical debridement of tissue.  The patients are also often severely ill and require hospitalization.

How common is Cellulitis?

Cellulitis is exceedingly common in the United States and frequently responsible for primary care and emergency department visits.  Cellulitis and abscesses are among the most common skin and soft tissue infections.  Severe cases often require hospitalization – this is commonly the case for patients with skin infection and diabetes.

Middle-aged and older adults are most often affected by cellulitis.  The incidence of cellulitis is approximately 200 cases per 100,000 patient-years.

What are the symptoms and signs of Cellulitis?

The most common symptoms of cellulitis include:

  • Spreading redness
  • Warmth
  • Pain
  • Swelling
  • Fever (Temperature > 101 F)

Occasionally purulent exudate (pus) will be draining from the site.  Abscesses are characterized by fluctuance, a shiny appearance, and potentially drainage of pus from a sinus tract.  These require surgical incision and drainage in addition to antibiotic therapy.  Another important consideration is whether or not you have had a tetanus vaccination in the past 10 years.  Patients may benefit from tetanus revaccination and may require tetanus toxoid under certain circumstances.

How is Cellulitis diagnosed?

The diagnosis of cellulitis is suggested based on symptoms and physical examination – typical findings include spreading redness, warmth, pain, swelling, and fever.  If you have a sinus tract that is draining pus, your doctor may obtain a sample and send it for gram stain and culture.  This is also typically performed when you have an abscess that requires incision and drainage.  The purpose of gram stain and culture is to guide antimicrobial therapy.  The laboratory will typically test bacterial growth against commonly prescribed antibiotics and determine resistance patterns.  Bacterial cultures generally take at least 2 days to return.

If your doctor suspects a more aggressive or serious infection, they may order an x-ray to evaluate for air in the wound (suggesting gas gangrene) and evidence of bone infection.  Sometimes an MRI needs to be obtained to definitively rule out bone infection.

A mild cellulitis typically does not requires blood tests but in severe forms of cellulitis, your doctor may order a CMP (comprehensive metabolic panel), CBC (complete blood cell count), inflammatory markers (ESR, CRP), lactate, and diabetes screening.

How is Cellulitis treated?

Cellulitis is treated with various antibiotics, which most often include:

Cellulitis associated with abscesses requires incision and drainage.  For this procedure, your doctor will likely clean the area with antiseptic solution such as Betadine (povidone-iodine) or ChloraPrep (chlorhexidine).  They will then typically anesthetize the area with 1% lidocaine using a needle and syringe.  The abscess will then be drained using a scalpel and hemostat to probe the pocket of pus and break up any loculations.

Severe skin and soft tissue infections accompanied by dead tissue, gas gangrene, or necrotizing fasciitis typically require intravenous antibiotics with surgical consultation for aggressive wound debridement.  The purpose of wound debridement is to remove any devitalized or dead tissue in the region – bacteria thrive in this environment.

Cellulitis Patient Summary:

  • Cellulitis is an infection of the skin. It typically occurs when there is an opening in the skin allowing bacteria to enter and proliferate in skin tissue.  
  • Bacteria are usually of the gram positive variety such as staphylococcus and streptococcus species.
  • Sometimes, aggressive strains of bacteria such as methicillin resistant S. aureus infect skin tissue – this often results in the formation of boils or abscesses.
  • Occasionally, bacteria such as Clostridium perfringens or Pseudomonas will be responsible for infection – especially in frequently hospitalized patients and those with diabetes.
  • The most common symptoms of cellulitis include spreading redness, warmth, pain, swelling, and fever (Temperature > 101 F).
  • The diagnosis of cellulitis is suggested based on symptoms and physical examination.
  • Severe forms of cellulitis often require blood tests such as CMP (comprehensive metabolic panel), CBC (complete blood cell count), inflammatory markers (ESR, CRP), lactate, and diabetes screening. Your doctor may also order an x-ray or MRI.
  • These cases may be associated with gas gangrene and tissue necrosis – death of skin tissue. These cases often require intravenous antimicrobial therapy and surgical debridement of tissue.
  • Cellulitis is treated with various antibiotics which most often include: Keflex (cephalexin), Augmentin (amoxicillin-clavulanate), Ancef (cephazolin), Tetracycline (doxycycline), Bactrim (trimethoprim-sulfamethoxazole), Clindamycin, Vancomycin, Zosyn (piperacillin-tazobactam).

References:

  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:e10.
  2. Miller LG, Daum RS, Creech CB, et al. Clindamycin versus trimethoprim-sulfamethoxazole for uncomplicated skin infections. N Engl J Med 2015; 372:1093.

Popular Cellulitis Medications

The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.