Psoriasis as we know it today was grouped with leprosy until the mid‐19th century. The two main histological features of psoriasis are inflammation and epidermal hyperplasia. More recently, it was shown in the 1950s that one form of psoriasis, guttate psoriasis, could be precipitated by streptococcal throat infections. It has recently been suggested that it is the microbiota in the skin that may be responsible. Since it has been possible, with the advent of molecular techniques, to investigate the microbiome in tissues, there have been studies on both normal skin and psoriasis that suggest that the microbiota may well be involved. All studies found the three most common phyla in psoriasis specimens and that from uninvolved skin and normal control skin to be Firmicutes, Actinobacteria and Proteobacteria. Interestingly, in a microbiome study of the blood in psoriasis patients the commonest genus was streptococcus in guttate psoriasis and Staphylococcus in chronic plaque psoriasi.