Cowpox and pseudocowpox are two antigenically and structurally distinct pox viral agents that cause skin infections of the teats and udders of cattle. Cowpox was once common in most countries of the world where cattle were raised, but as incidence of smallpox (thought to be naturally connected with cowpox) decreased in the human population due to vaccination, the incidence of cowpox in the bovine population also decreased. Most pox-like infections in cattle around the world today are thought to be caused by pseudocowpox, which is a relatively common cattle infection. Transmission to man is primarily by direct contact with lesions on cattle. Pseudocowpox infections in man are termed 'milker's nodules' or 'milker's wart'. The infection begins with a lesion which progresses from a papule to a vesicle surrounded by erythema and oedema. The lesions develop into firm, elastic nodules which usually heal spontaneously in four to six weeks. There is no specific treatment but topical antibiotic treatments are sometimes helpful.