Biophoto Associates / SCIENCE PHOTO LIBRARY Diagnosis of Seborrheic Dermatitis Clinical evaluation Diagnosis of seborrheic dermatitis is made by physical examination. Seborrheic dermatitis of the scalp must be differentiated from other disorders: Atopic dermatitis of the scalp: This disorder typically first manifests with fine, white, dry scaling rather than the greasy yellowish scale of seborrheic dermatitis.