Aims. The inadequate provision of allergy services in the United Kingdom is attributed, in part, to poor undergraduate teaching of the subject. We ascertained the level of medical student knowledge about allergy, an extremely common disease, and congenital heart disease, an important yet rare condition, to see if the focus of medical student teaching was correctly matched to disease burden within the general population. Methods. An online quiz was designed consisting of 10 questions on common allergy problems and 10 questions on congenital heart disease to be taken by medical students. Results. Two hundred and fourteen respondents took the quiz, the majority (78.5%) of who were clinical medical students. There was a significant difference between the mean scores for the allergy (µ = 28.7%, standard deviation = 15.5) and congenital heart disease (µ = 40.1%, standard deviation = 21.3) sections; t(213) = −6.78, P < .0001. Discussion. Knowledge about basic allergic disease was very poor within a medical student population. Mean percentage scores were significantly reduced when compared to questions concerning the rare and infrequently encountered condition of congenital heart disease. We question the wisdom of undue emphasis on certain rarely encountered conditions against common, equally important conditions in medical school teaching.