INTRODUCTION
Acne vulgaris is a common, multifactorial disease characterized by 4 pathophysiologic processes: 1) presence and activity of bacteria, 2) inflammation, 3) excess sebum production, and 4) excess keratinization.1
Clinically, acne is characterized by the formation of comedones, papules, and pustules. Acne involves the pilosebaceous unit of the skin and typically occurs where the sebaceous glands are largest and most active. Acne treatments target 1 or more of the mechanisms believed to be responsible for causing acne. Antibiotics and topical agents such as benzoyl peroxide (BPO) target the bacteria Propionibacterium acnes. Anti-inflammatory agents target 1 or more of the many inflammation pathways that are interrelated with bacterial activities. Other agents have putative actions that stop or decrease the excessive sebum production typically associated with androgens. Topical retinoids normalize the abnormal keratinization process.
Available acne treatments have remained relatively constant for decades, with antibiotics being the typical first line of treatment. Newer therapies including combination therapy with retinoids and BPO have the highest treatment success.2 Among the reasons for suboptimal treatment results are bacterial resistance and insufficient targeting of inflammatory pathways.3-5
Zinc is a trace element that is necessary for many physiologic processes, including gene transcription, phagocytic activity of macrophages, and stabilization of biological membranes.1,6 Zinc is also a modulator of the wound-repair process.7 Other beneficial effects, such as antioxidant and anti-inflammatory properties, have been attributed to zinc, including as a treatment for psoriasis, hair loss, leg ulcers, wound healing, and acne.6,8,9
In acne treatment, zinc has been linked with decreasing sebum production, decreasing anti-inflammatory mediators, and with antibacterial effects on P acnes,3,7,10-21 although its role in acne therapy has been seen as controversial. This systematic review examines the published literature pertaining to oral or topical zinc’s effectiveness as a treatment for acne vulgaris.
METHODS
A literature search was conducted in MEDLINE, Google Scholar, and the Cochrane Library for articles published in English over the past 30 years. The search terms were “acne,†“zinc,†“topical,†and “skin.†Individual articles identified as relevant and pertaining to the scope of this review were rated for quality based on Strength of Recommendation Taxonomy (SORT) criteria (Table 1).22 Some of the criteria that specify a stronger rating, a lower number score, include randomized, double-blind, large number of subjects, placebo controlled, and proper patient population. Level 1, the highest rating using the SORT criteria, is reserved for well-designed studies that have patient-oriented evidence as the key outcome. A SORT strength of recommendation was then given to the body of evidence for oral and topical zinc (Table 2).
