Carl Emanuel Flemming Rasch (7 February 1861 – 6 July 1938) was a Danish dermatologist and venereologist who in 1900 coined the term "polymorphic light eruption", following his studies of the effect of sunlight on the skin.

[2] Thomas Bateman had described, based on findings by Robert Willan,[4] what he called "eczema solare", in the early 19th century, a condition caused by the action of sunlight on abnormally reacting skin.

[5] Rasch's interest in "the action of sunlight on the skin" led him, in 1900, to describe this same condition as "eczema-like polymorphic light eruption".

He performed a Wassermann test, confirming Syphilis and she subsequently commenced treatments including arsenic, mercury and salvarsan.

[19] Her medical history and communication with physicians have been a matter of debate by her biographers and she did not disclose her secret use of laxatives, amphetamines and fear of gaining weight.

[21] He had a large collection of copperplate prints, the proceeds of the sale of which he bequeathed to the Dermatology Society, to be used particularly for the travel expenses of young Danish dermatologists.