How does the sle butterfly rash develop?

Inflammation: Systemic lupus erythematosus, sle, lupus, is an auto-immune disorder in which a person's immune system is reacting strongly against parts of his own body. The inflammation caused by the immune system reaction (hypersensitivity reaction) leads to the lupus symptoms, including the butterfly rash (malar rash). The rash is more likely to occur, and seems to worsen, after exposure to sunlight.

Malar Rash: The malar rash of lupus is red or purplish and mildly scaly. Characteristically, it has the shape of a butterfly and involves the bridge of the nose. Notably, the rash spares the nasolabial folds of the face, which contributes to its characteristic appearance. It is usually macular with sharp edges and not itchy. Sun exposure can worsen the rash.