DP1-mediated responses include inhibition of platelet aggregation, vasorelaxation and bronchodilatation [7], but DP1 antagonists have also been found to ameliorate rhinitis, conjunctivitis and pulmonary inflammation in animal models [8,9,10], while DP1 receptor activation aggravated neutrophil infiltration in acute lung injury [11]. Here, PTGDR is linked to conjunctivitis.