The severity of acne vulgaris (Gr. ἀκµή, "point" + L. vulgaris, "common") can be classified as mild, moderate, or severe to determine an appropriate treatment regimen. There is no universally accepted scale for grading acne severity. The presence of clogged skin follicles (known as comedones) limited to the face with occasional inflammatory lesions defines mild acne. Moderate severity acne is said to occur when a higher number of inflammatory papules and pustules occur on the face compared to mild cases of acne and appear on the trunk of the body. Severe acne is said to occur when nodules (the painful 'bumps' lying under the skin) are the characteristic facial lesions, and involvement of the trunk is extensive.