Background: There is a long history of using topical coal tar for the treatment of psoriasis and atopic dermatitis (AD).
Objective: To review the literature on coal tar and its derivatives, without the use of ultraviolet light, for the treatment of psoriasis or AD.
Methods: MEDLINE/PubMed and Cochrane Database of Systematic Reviews literature searches were performed to identify randomized controlled trials and clinical trials of topical coal tar for the treatment of psoriasis or AD. Studies were graded according to a modified version of Sackett's criteria for clinical evidence and evaluated to determine if they support or do not support the use of coal tar therapy.
Results: Twenty-five studies meeting the authors' search criteria were identified, only two of which were placebo-controlled. The majority (21, or 84%) supported the use of coal tar products in the treatment of psoriasis or AD, while four (16%) did not support the use of coal tar products.
Conclusion: Most studies support the use of coal tar products, although their level of evidence is not strong. Topical coal tar was found to be efficacious in the treatment of psoriasis in two placebo-controlled trials. Coal tar products appear to be therapeutic in psoriasis and AD, are well tolerated with few side effects, and are cost-effective. Staining and odor are deterrents to coal tar therapy. Large, randomized, double-blind, placebo-controlled studies with precise point estimates of treatment effect are needed to establish the efficacy of coal tar preparations.