The mechanism of the development of berlock dermatitis has been the subject of repeated investigations since the first cases of this disorder were described by Freund. From these investigations has come the idea that oil of bergamot, which is one of the essential oils in eau de cologne and other perfumes, in some manner sensitizes the skin to the rays of the sun and thereby causes inflammation of the skin, which is usually followed by brownish pigmentation in the involved areas.
Freund and many investigators after him realized the therapeutic possibilities of the use of oil of bergamot, either alone or in alcoholic solution, combined with sunlight or ultraviolet irradiation, to produce pigmentation, in areas of the skin which had lost their normal content of pigment, as in vitiligo. Conflicting results have been reported.
In none of the investigations were the changes in color which took place recorded by
ROGIN JR, SHEARD C. FACTORS AFFECTING COLOR OF THE SKINTHEIR SIGNIFICANCE IN BERLOCK DERMATITIS. Arch Derm Syphilol. 1935;32(2):265–283. doi:10.1001/archderm.1935.01470020087009