These recommendations are consistent with Guidelines on the management of cellulitis, published by the Clinical Resource Efficiency Support Team (CREST) [CREST, 2005].

• There is generally a lack of evidence from placebo controlled trials to support the effectiveness of antibiotics in the treatment of cellulitis, but limited evidence from comparative trials indicates that the appropriate antibiotic will successfully treat cellulitis in about 85% of cases [Jones, 2002].
• The choice of antibiotic should be guided by known antibiotic sensitivities to the likely causative pathogens:
• Flucloxacillin is a relatively narrow-spectrum antibiotic licensed for the treatment of cellulitis [ABPI Medicines Compendium, 2008]. It demonstrates suitable pharmacokinetics, with good diffusion into skin and soft tissues [Finch et al, 2003] and, at high doses, is active against the large majority of staphylococcal and streptococcal species that cause cellulitis [CREST, 2005].
• Erythromycin is a macrolide antibiotic with a broad spectrum of activity and is suitable (and licensed) as an alternative to flucloxacillin, for example in people with an allergy to penicillin. The spectrum of activity of erythromycin includes activity against most staphylococcal species (including Staphylococcus aureus) and some Gram-negative cocci and anaerobes which may be implicated [Finch et al, 2003].
• Clarithromycin is licensed and recommended by CREST as an alternative to flucloxacillin [CREST, 2005], and has a similar spectrum of activity as erythromycin, but is reputed to cause fewer adverse effects [DTB, 1991]. The perceived superior adverse effect profile of clarithromycin compared with erythromycin is mainly theoretical, although there are some limited data from randomized controlled trials to corroborate it [Aronson, 2006].
• Co-amoxiclav is recommended by the Health Protection Agency for treatment of facial cellulitis in primary care [HPA and Association of Medical Microbiologists, 2008].
• Ciprofloxacin is recommended by CREST in addition to flucloxacillin (or a macrolide) if the cellulitis has arisen from a wound contaminated with fresh (un-chlorinated) water [CREST, 2005]. This is to cover the possibility of infection with aeromonas species [Swartz, 2004].
• Doxycycline should be considered, in addition to flucloxacillin (or a macrolide), if there has been contamination with salt water, to cover the possibility of infection with Vibrio vulnificus [Swartz, 2004].
• Clindamycin is an option recommended by the Health Protection Authority for the treatment of cellulitis in people who are allergic to penicillin [HPA and Association of Medical Microbiologists, 2008]. However, it has a worse adverse effect profile than the macrolides [BNF 55, 2008], so should be considered second-line.