• This guideline is for patients aged greater than or equal to 12 years with cellulitis and supersedes the EAS cellulitis guideline.
• Use this guideline in conjunction with the relevant ECP guideline if the patient has cellulitis secondary to a mammal bite or if an abscess is present.
• Use this guideline in conjunction with the relevant EAS guideline if the patient has sepsis.

Assessment

• Take a history and perform a physical examination, including an assessment of:
  • Causes and risk factors for cellulitis.
  • Signs of systemic involvement.
  • Acute complications of cellulitis.
  • Differential diagnoses.
  • Features in the transport/referral criteria.
• A swab for microbiology is not routinely required. Swab only if:
  • There is significant discharge.
  • The lesion is not improving or is deteriorating.
  • The presence of MRSA is suspected.
  • Empiric antibiotic treatment has failed.
• Mark the outer margins of the erythema as a baseline for future reference.
• Determine cellulitis severity, using the assessing cellulitis severity table.

Assessing cellulitis severity table

Management

Mild cellulitis

• Supply antibiotics for five days:
  • For an adult supply 500 mg flucloxacillin PO four times daily.
  • For a child supply 12.5 mg/kg flucloxacillin PO four times daily, or
  • If the patient has an allergy to penicillin or flucloxacillin is not preferred:
    • For an adult supply 1000 mg cefalexin PO twice daily, or
    • For a child supply 12.5 mg/kg cefalexin PO to a maximum dose of 1000 mg twice daily.
  • See the paediatric drug dose tables for the exact doses for a child.

Moderate cellulitis

• Supply antibiotics for seven days:
  • For an adult supply 1000 mg flucloxacillin PO four times daily.
  • For a child supply 25 mg/kg flucloxacillin PO four times daily, or
  • If the patient has an allergy to penicillin, or flucloxacillin is not preferred:
    • For an adult supply 1000 mg cefalexin PO three times daily, or
    • 300 mg roxithromycin PO once daily.
    • For a child supply 25 mg/kg cefalexin PO to a maximum dose of 1000 mg twice daily, or
    • Supply 5 mg/kg roxithromycin PO to a maximum dose of 300 mg once daily.
  • See the paediatric drug dose tables for the exact doses for a child.

Severe cellulitis

• Consider immediate referral to an ED.
• Consider eligibility for a community IV antibiotic regimen such as cefazolin and oral probenecid, providing a local pathway is available.
• If the patient is being managed in the community and there is any delay in pursuing a local pathway for IV antibiotics, supply oral antibiotics for moderate cellulitis, and:
  • For an adult administer 1 g cefazolin IV.
  • For a child see the EAS paediatric drug dose tables for the dose of cefazolin IV.
• Monitor the patient for at least 20 minutes after administration of antibiotics IV.

Transport/referral criteria

• The patient requires immediate referral to an ED by ambulance:
  • Suspected necrotising fasciitis.
  • Inability to mobilise.
  • Temperature > 40°C.
  • Sepsis with any clinical feature indicating antibiotics (see the relevant EAS guideline for these features).
• The patient requires referral to an ED, however alternative transport may be appropriate:
  • Features of severe cellulitis.
  • Sepsis with two or more features of concern (see the relevant EAS guideline for these features)
  • Extensive or severe oedema.
  • Immunocompromised (for example, on steroids or immunotherapy).
  • Neutropenic.
  • Chemotherapy within the last four weeks.
  • Associated with an abscess requiring surgical drainage.
  • Rapidly spreading.
  • Periorbital, facial, neck, hand or genital location.
  • Associated with a diabetic foot ulcer.
  • Significant lymphangitis.
  • Frail, elderly or significant comorbidities.
  • Significant vomiting.

Advice

Provide the following information and advice to patients managed in the community.

• Keep the affected area elevated (if possible) for comfort and to relieve oedema.
• Redness and swelling may continue to extend outside the marked area in the first 1-2 days even if treatment is appropriate.
• Provide a cellulitis patient information leaflet.
• Take oral analgesia as required.
• To control the infection, the antibiotics must be taken regularly.
• Arrange for review of response to treatment in two days.
• Seek medical attention earlier if:
  • Cellulitis spreads significantly 24 hours after starting antibiotics.
  • There are signs of sepsis.
  • The patient develops severe pain.
  • The patient develops vomiting.

Additional information

General principles

• Cellulitis is an acute, bacterial infection of the lower dermis and subcutaneous tissue most commonly affecting the lower limbs in adults.
• Cellulitis is characterised by unilateral localised pain, swelling, erythema and heat. Patients may also present with fever, malaise and in severe cases oedema, blisters, ulcers and lymphangitis.
• Cellulitis usually begins with a breach in the skin, noting that the breach may be tiny and difficult to locate. Causes of cellulitis include:
  • Dry, cracked skin.
  • Eczema.
  • Tinea pedis.
  • Cuts or other wounds.
  • Burns.
  • Insect bites or stings.
  • Surgery.
  • IV cannulation.
• Common pathogens responsible for cellulitis include:
  • Streptococcus pyogenes.
  • Staphylococcus aureus.
  • Group C or Group G streptococci.
• Risk factors for cellulitis include:
  • Obesity.
  • Diabetes.
  • Pregnancy.
  • Venous insufficiency.
  • Peripheral artery disease.
  • Ulcers.
  • Lymphoedema.
  • History of previous cellulitis or erysipelas.
• Risk factors for a poor outcome secondary to cellulitis include:
  • Advanced age.
  • Frailty.
  • Diabetes.
  • Impaired renal function.
• Community management in most uncomplicated cellulitis begins with high dose oral antibiotics.
• Acute complications of cellulitis include:
  • Necrotising fasciitis.
  • Myositis.
  • Subcutaneous abscesses.
  • Septicaemia.
  • Post-streptococcal nephritis.

Differential diagnoses for cellulitis

• DVT.
• Septic arthritis.
• Gout.
• Ruptured Baker’s cyst.
• Thrombophlebitis.
• Cutaneous abscess.
• Metastatic cancer.
• Chronic conditions that are usually bilateral but may present with superimposed cellulitis include:
  • Varicose eczema or venous insufficiency.
  • Lipodermatosclerosis.
  • Cutaneous small vessel vasculitis.
  • Oedema with or without blisters.

DVT

• Exclude DVT before electing to manage unilateral localised pain, swelling, erythema and heat in a lower limb as cellulitis.
• DVT is the most common alternative diagnosis for patients who present with unilateral leg swelling and erythema. Where it cannot be confidently excluded, the patient should be referred.

Cellulitis in children

• Cellulitis is uncommon in children.
• Have a low threshold for recommending transport to an ED.
• Have a low threshold for seeking clinical advice before commencing treatment in a child.

Necrotising fasciitis

• Necrotising fasciitis is a rare but important differential that must be confidently excluded before making the decision to manage cellulitis in the community.
• Necrotising fasciitis is a rapidly progressing soft tissue infection with a high mortality rate characterised by extensive and progressive necrosis of the subcutaneous tissue and fascia.
• Extreme tenderness, dusky (not red or pink) discolouration, more severe illness, high fever, tachycardia and hypotension assist in differentiating necrotising fasciitis from cellulitis.

Erysipelas

• Erysipelas is a superficial form of cellulitis affecting the upper dermis and presents with bright red clearly demarcated inflammation.
• It may coexist with cellulitis and is treated in the same way.

Antibiotic treatment

• Antibiotic treatment is required for all patients with cellulitis.
• Oral antibiotic treatment is appropriate for those with mild to moderate cellulitis.
• IV antibiotic treatment is usually required for patients with severe cellulitis or those not responding to oral treatment despite concordance with the treatment regimen.
• Consider administering a further dose of IV antibiotics on follow up if:
  • The cellulitis is not significantly improving, and
  • The patient is not immediately being referred to an ED.
• The optimal duration of oral antibiotic treatment is uncertain due to a lack of clinical trials and published guidelines, but range from 5-10 days. In general, antibiotics should be taken until cellulitis has cleared.
• The expectation is that clinical review of the response to the initial antibiotic regimen will be conducted by the patient’s usual primary care provider who will make the decision about the antibiotic course duration.

Reassessment

• Include an assessment of the response to treatment only if appropriate treatment has been commenced greater than 24 hours ago.
• Patients may experience an increase in erythema and swelling within the first 48 hours of treatment even if the antibiotics are going to successfully control the infection.
• Evidence that the infection is being brought under control (despite the area of erythema remaining unchanged or enlarging) is indicated in most patients by:
  • Reduction in pain.
  • Improvement in appetite.
  • Increase in energy levels.
• Assess treatment concordance in patients who are not responding as well as expected. This includes assessing whether the patient is:
  • Resting and elevating the limb as instructed, and
  • Concordance with the antibiotic dosing regimen.
• Overall deterioration in condition (for example, increasing fever or tachycardia) is a more reliable indication of the need to escalate treatment rather than changes in the size of erythema.

Referral from EAS

• Patients referred under the relevant EAS guideline will typically:
  • Have mild to moderate cellulitis, and
  • Can be seen by an ECP within 12 hours, and
  • Require antibiotic treatment.
• EAS personnel may or may not have administered cefazolin IV.
• Administer PO antibiotics if indicated by this ECP cellulitis guideline even if the patient has received cefazolin IV.
• Timing:
  • Review for consideration of PO antibiotics should occur within 12 hours of EAS referral.
  • General review (rather than a referral to immediately start PO antibiotics) should not occur earlier than 24 hours after referral:
    • Cellulitis may take 24-36 hours to show any significant improvement.
    • Assessments for review should be delayed unless there are concerns about potential rapid
    deterioration.