Ten Cellulitis Myths Busted

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This was a fun article that searched the literature and dispensed with 10 myths about cellulitis.

Why does this matter?
Admissions for cellulitis have a huge economic impact and use valuable bed space in the hospital.  And it is often misdiagnosed.  Accurate diagnosis may reduce admissions and improve antibiotic stewardship.

Man, that looks red!
Myth 1 - Red = cellulitis

  • Stasis dermatitis, DVT, gout, allergic reactions, and other skin conditions are also red.
  • Elevation of the limb 45 degrees for 2 minutes will often make redness fade in most non-infectious causes, but redness will remain in cellulitis.

Myth 2 - My patient has bilateral leg cellulitis.

  • This is exceedingly rare.  There would have to be simultaneous inoculation of both legs.
  • It's probably stasis dermatitis or something else.

Myth 3 - All skin infections need antibiotics.

  • Very small abscesses may not need antibiotics.  (But see this NEJM paper we will cover later this month...)
  • Small areas of erythema, < 5 cm, may also not need antibiotics, especially if no systemic signs and not diabetic or immunocompromised.

Myth 4 - All skin infections need MRSA coverage.

  • Skin infection confirmed to not have an abscess does not benefit from adding TMP/SMX to cephalexin.
  • Furuncles should have MRSA coverage.
  • Consider your local infection patterns and the patient's risk for MRSA.

Myth 5 - Admissions for cellulitis need MRSA coverage.

  • See Myth 4 discussion.
  • If patients are systemically ill, an antibiotic with MRSA coverage is not a bad idea.

Myth 6 - Clindamycin will cover MRSA.

  • It depends on local resistance patterns at your facility.  Resistance may be as high as 35% in some areas.
  • Most MRSA strains remain sensitive to TMP/SMX and doxycycline.

Myth 7 - One also needs to add coverage for gram-negatives and anaerobes.  Maybe, but only if:

  • "Intensive care unit (ICU) level of care
  • Concern for bloodstream or necrotizing infection
  • Peri-rectal involvement, peri-orbital involvement, human or animal bite, surgical wound infection, traumatic aquatic injury, or osteomyelitis
  • Chronic diabetic foot wounds
  • Intravenous illicit drug use
  • Presence of neutropenia or severe cell-mediated immunodeficiency

Myth 8 - If redness goes beyond the margin previously traced out, it is getting worse.

  • This may be true, but in the first 48 hours, infection may spread a little while on antibiotics.
  • Spreading redness and fever should be considered a treatment failure if beyond 48 hours on antibiotics.

Myth 9 - Repeat infection will not happen in patients taking antibiotic prophylaxis.

  • Not true.
  • If skin is cracked, fungal infection is present, or chronic edema remains, infection may still recur.

Myth 10 - Redness around tick bites indicates cellulitis.

  • This is most often an inflammatory response to the bite.
  • Be wary of erythema migrans in Lyme-endemic areas.

Source
Top 10 Myths Regarding the Diagnosis and Treatment of Cellulitis.  J Emerg Med. 2017 Jul 3. pii: S0736-4679(17)30436-5. doi: 10.1016/j.jemermed.2017.05.007. [Epub ahead of print]

Another Spoonful
Don't miss this core knowledge post on emDocs, Cellulitis Mimics.

Peer reviewed by Thomas Davis, MD.

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