Anaphylaxis is a life-threatening emergency that may necessitate admission to a critical care unit. There are no reports of the frequency of admission to critical care units for patients with anaphylaxis or indeed any description of their demographic characteristics or outcomes. We analysed all physician-diagnosed cases of anaphylaxis over a 5-year period in national audit data from critical care units across the UK. Over the period 2005–2009, there were 81 paediatric and 1269 adult admissions with anaphylaxis admitted to UK critical care units (0.1% of admissions to paediatric units and 0.3% of admissions to adult units). Absolute numbers in both children and adults rose year on year. There were comparable proportions of admissions in female and male children (female = 47% and male = 53%; rate ratios (RR) = 0.88, 95% CI 0.64–1.20), but a greater proportion of adult female admissions (female = 65% and male = 35%; RR = 1.83, 95% CI 1.68–1.99). Survival to unit discharge was 95% (77/81) for children, and survival to hospital discharge was 92% (1166/1269) for adults. Each UK critical care unit is likely to see at least one anaphylaxis case per year. The number of admissions has risen in both children and adults. Although admission ratios between the sexes were comparable in children, there was a female preponderance in adult life. Survival rates were high at over 90%.