“…Lung mast cells generate prostaglandin D2 (PGD2) in vitro following calcium ionophore A23 187-and IgE-dependent activation (Holgate et al, 1984). Evidence ofPGD2 generation by human skin derives from experiments in vivo in which local provocation of cold or heat urticaria and anaphylaxis is accompanied by a rise in venous plasma histamine or PGD2 concentrations (Heavey et al, 1986;Koro et al, 1986;Barr et al, 1986). The precise function of released PGD2 in the skin is not known, although recent studies have shown it to be a weak vasodilator in the human cutaneous vasculature (Beasley et al, 1987) and it is also a weak chemokinetic agent in human leukocytes (Goetzl et al, 1976) causing neutrophil accumulation when injected 'Author for correspondence at: Clinical Pharmacology, CF104, Centre Block, Southampton General Hospital, Southampton S09 4XY. intradermally (Soter et al, 1983).…”