There are many similar conditions that require diagnosis differentiation. However, seborrheic dermatitis varies in severity, usually related to stress, while the later is a stable condition. Dandruff has not been associated with inflammation however, seborrheic dermatitis has been correlated with erythema and crusting. Psoriasis vulgaris of the scalp has been difficult to distinguish from seborrheic dermatitis. Seborrhea is found generally on the face with greasy thick yellow scales and psoriasis is found generally on the elbows and knees with a dry and silvery look.
Atopic dermatitis involves more itching and if located at the folds of the arms and knees.
Asthma and hay fever usually precede this recurrent condition. Seborrheic Dermatitis References 1.