Retinoids are medications which reduce inflammation, normalize the follicle cell life cycle, and reduce sebum production.[45][83] They are structurally related to vitamin A.[83] Studies show they are underprescribed by primary care doctors and dermatologists.[15] The retinoids appear to influence the cell life cycle in the follicle lining. This helps prevent the accumulation of skin cells within the hair follicle that can create a blockage. They are a first-line acne treatment,[1] especially for people with dark-colored skin, and are known to lead to faster improvement of postinflammatory hyperpigmentation.[36]
The severity of acne vulgaris (Gr. ἀκµή, "point" + L. vulgaris, "common")[24] can be classified as mild, moderate, or severe as this helps to determine an appropriate treatment regimen.[20] There is no universally accepted scale for grading acne severity.[15] Mild acne is classically defined by the presence of clogged skin follicles (known as comedones) limited to the face with occasional inflammatory lesions.[20] 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 are found on the trunk of the body.[20] 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.[20][25]
The recognition and characterization of acne progressed in 1776 when Josef Plenck (an Austrian physician) published a book that proposed the novel concept of classifying skin diseases by their elementary (initial) lesions.[164] In 1808 the English dermatologist Robert Willan refined Plenck's work by providing the first detailed descriptions of several skin disorders using a morphologic terminology that remains in use today.[164] Thomas Bateman continued and expanded on Robert Willan's work as his student and provided the first descriptions and illustrations of acne accepted as accurate by modern dermatologists.[164] Erasmus Wilson, in 1842, was the first to make the distinction between acne vulgaris and rosacea.[165] The first professional medical monograph dedicated entirely to acne was written by Lucius Duncan Bulkley and published in New York in 1885.[166][167]

Acne treatment that you apply to the skin: Most acne treatments are applied to the skin. Your dermatologist may call this topical treatment. There are many topical acne treatments. Some topicals help kill the bacteria. Others work on reducing the oil. The topical medicine may contain a retinoid, prescription-strength benzoyl peroxide, antibiotic, or even salicylic acid. Your dermatologist will determine what you need.