Munch's treatment of colour, and brushwork in this is quintessentially . The colour scheme is dominated by the relationship of a range of sea-greens with a hot orange-red, which Munch has even used for his signature. It may be suggested that the greens and reds themselves evoke the queasiness and fever of illness and the effect of the colour scheme is intensified by the fact that these colours are whose dynamic effect in combination, of simultaneous contrast and affinity, is here being exploited for emotional as well as aesthetic effect. The girl's face glows, almost as if from within, with a pale yellow light of fever. In fact, this almost unearthly light, which is also reflected strongly from the bedhead to form a stark background to the two heads, must come from the window just visible at the right edge of the . The very dark dress of the woman forms an area of strong contrast which acts as a foil, intensifying perception of the rest of the picture. Its funereal blue-black reinforces the feeling of grief which Munch has stated with great economy of means simply through the woman's bowed silhouette. The brushwork is rapid and agitated. This painting is the fourth of six versions in oil that Munch made of this subject, the first dating from 1885-86. Munch later wrote 'In the sick child I opened for myself a new path - it was a breakthrough in my art. Most of what I have done since had its birth in this picture'.
What is understood of the inspiration of 'The Sick Child' is extremely interesting. It appears to have some reference to the death from tuberculosis in 1877, at the age of fifteen, of Munch's elder sister Johanne Sophie. This theory is supported by the identification of the woman by the bed as Munch's aunt, Karen Bjolstad, who looked after the children after their mother died. However, the immediate inspiration for the painting, in 1885, came when Munch accompanied his father, who was a doctor, on a visit to a boy of five who had broken his leg. The boy's sister Betzy was sitting in the sickroom broken down with grief at the pain the boy was experiencing. Munch appears to have been forcibly struck with this and asked permission to paint Betzy. She then became the sick child and the image of her grief was transferred to the attendant aunt. It seems that Munch used the immediate experience of the episode of the visit to evoke and paint the much more deeply personal trauma of his sister's death eight years previously.
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.122