To tan skin is to brown it, dye it, transform its properties. Whether one refers to the process of turning raw hide to treated leather (the verb’s etymological origins), or that of pigmenting human skin from pallid whiteness to a bronzed, luxurious surface, the concept of tanning remains the same. In contributing to this edited volume on skin and its medical histories, this chapter focuses on an under-explored topic in early twentieth-century medicine: bodily exposure of tubercular patients to light, or, perhaps better put, a therapeutics of tanning. From the early 1890s onwards, physicians internationally became increasingly fascinated by the natural healing powers of light. e primary, though not sole, target of both heliotherapy (natural sun therapy) and phototherapy (arti - cial light therapy) was to treat tuberculosis in its various manifestations. is included pulmonary tuberculosis, Pott’s disease, scrofula, bone and joint (‘surgical’) tuberculosis, and lupus vulgaris (tuberculosis of the skin). Heliotherapists and phototherapists sought to rid the body of tubercle bacilli, heal the dis guring and suppurating wounds caused by them, and prevent further recurrences by building up the patient’s physiological defences. For these physicians, light had the miraculous, natural ability to conquer the ravages of disease. Directed onto the patient’s skin, natural sunlight and arti cial light were perceived to stimulate the body’s mechanisms, the tissues, organs and blood, and those internal

processes were signalled by external signs occurring on the surface, most notably through the ongoing pigmentation of the skin.