Skyrin is a bright orange mycotoxin pigment first reported from Penicillium islandicum but since reported in a broad cross-section of fungal genera and lichens. Its name is derived from skyr, an Icelandic bacterial soured milk, a mouldy sample of which provided the Sopp type strain of P. islandicum. Skyrin is a bisanthraquinone which degrades to two molecules of emodin on treatment with sodium dithionite. Its structure was resolved by Shibata and co-workers in 1955. Skyrin is an important metabolite for the detection of mycotoxins.