[2][3] This is also known as an autoeczematous response[4] and there must be an identifiable initial inflammatory or infectious skin problem which leads to the generalised eczema.

Often intensely itchy, the red papules and pustules can also be associated with blisters and scales and are always remote from the primary lesion.

[8] Potential explanations include Although there are a multitude of varying appearances, the id reaction often presents with symmetrical red patches of eczema with papules and vesicles, particularly on the outer sides of the arms, face and trunk which occur suddenly and are intensely itchy occur a few days to a week after the initial allergic or irritant dermatitis.

[2][3] The diagnosis is frequently made by treating the initial triggering skin problem and observing the improvement in the eczematous rash.

[2] Initial tests may include isolating a fungus by taking a swab and sending it for culture.

[2] Id reactions are frequently unresponsive to corticosteroid therapy, but clear when the focus of infection or infestation is treated.

German dermatologist Josef Jadassohn (1863–1936), who coined the term id, had observed a dermatophytosis causing a secondary allergic skin dermatitis.