Estimating the percentage of skin involvement within a body area. (A) NIH scoring of erythema for the NIH anterior torso body area (dark blue dashed line) involves dividing the area into fourths using your mind's eye, drawing a line of best fit across the lower edge of erythema, to arrive at ~ 70% involvement. (B) VSS of erythema for the anterior torso involves scoring for 2 body areas. The chest body area (dark blue dashed line) is 100% involved. The abdomen and genitalia body area (light blue dashed line) is divided into thirds using your mind's eye, and a line of best fit across the lower edge of erythema leads to ~ 35% involvement.