The patient, an 82 year old Caucasian woman, was admitted to hospital with confusion. She had a number of active medical problems, including atrial fibrillation, ischaemic heart disease, chronic kidney disease, hypertension and osteoarthritis. Six years prior to admission she had undergone a right hemicolectomy for Dukes B colorectal carcinoma.

During admission she was diagnosed as having a urinary tract infection (UTI). Prior to admission her general practitioner had treated the patient with a 3 day course of trimethoprim 200 mg bd. On admission to hospital, urine culture was positive for Escherichia. coli and she was prescribed a 5 day course of oral co-amoxiclav 625 mg tds. Four days following completion of this course of antibiotics, she developed diarrhoea, which was positive for Clostridium difficile toxin. Metronidazole 400 mg tds was prescribed immediately. The patient's diarrhoea worsened, she was opening her bowels 7 times daily with a Bristol Stool classification Type 7 stool. After five days of oral metronidazole therapy, oral vancomycin 250 mg qds was started.

Four days after oral vancomycin therapy was instigated, the patient developed a widespread pruritic, confluent, erythematous rash over her chest, back, neck and thighs. She also complained of a severe headache. Dermatology review was requested and the opinion was that the rash appeared to be like that seen in 'Red Man Syndrome'. It was confirmed with nursing staff that no drug errors had been made and no vancomycin had been administered intravenously in error.

Vancomycin therapy was stopped immediately and regular antihistamines were prescribed. The rash then cleared and did not return. Rechallenge with oral vancomycin was not initiated. No other drug therapy was altered during this time, and no other potential allergens could be indentified.

On admission the patient had Chronic Kidney Disease (CKD) stage 2. When she developed C. difficile diarrhoea the patient developed acute-on-chronic renal failure, with renal function deteriorating to an equivalent of CKD stage 3. Some case reports of patients developing 'Red Man Syndrome' in association with oral vancomycin therapy have involved patients with impaired renal function, suggesting that reduced excretion of any systemically absorbed vancomycin may contribute to developing the reaction. Unfortunately, despite our request, vancomycin levels were not performed by our laboratory.

The reaction seen in our patient seemed to be the same as that seen previously with intravenous vancomycin administration ? the 'Red Man Syndrome'. Review of the literature reveals a number of existing case reports describing rashes during oral vancomycin therapy, including one case of measurable serum vancomycin levels. All cases we became aware of have been described in patients in the presence of colitis or impaired renal function.

As described, this reaction is thought to be associated with intravenous administration of the drug, but there are isolated case reports of 'Red Man Syndrome' in association with intraperitoneal and oral administration of vancomycin [⁸,¹⁰,¹¹].

With increasing incidence of C. difficile pseudomembranous colitis, and the increased use of oral vancomycin therapy to treat it, reporting of cases of possible 'Red Man Syndrome' is essential. From our literature review, cases have only been reported in patients with an inflammatory bowel process. It cannot necessarily be concluded that inflammatory bowel processes are required to allow the absorption of vancomycin. It is true that it is only in these cases possible 'Red Man Syndrome' has been reported but oral vancomycin has few indications for use.

It causes us to question the mechanism of this drug reaction. Does the presence of an inflammatory bowel process allow vancomycin absorption, resulting in significant serum concentrations of the drug, made more significant if there is reduced renal excretion? Alternatively, is the presence of vancomycin in the gut able to cause histamine release without systemic absorption? With increasing use of oral vancomycin, recording of possible 'Red Man Syndrome', with measurement of serum vancomycin concentrations, is essential.

Written informed consent was obtained from the patient for publication of this case report. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

The authors declare that they have no competing interests.

HG collected the details of the case and recorded the patient data including microbiology specimens and renal function. PB was the major contributor in researching and writing the manuscript. Both authors read and approved the final manuscript.