You may find it hard to tell between seborrheic dermatitis and psoriasis, but there are some markers of difference. As Jane explains, "With seborrheic dermatitis, you may develop the condition in other areas where you have sebaceous activity, such as your eyebrows or your groin, wherever there is hair. With psoriasis , you may get it anywhere: your back, your elbows or even your knees. But not every person experiences this in areas other than the scalp."