No increased risk of cancer

• In 2010 The Journal of Investigative Dermatology published a large cohort study involving 13,200 patients with psoriasis and eczema which found that coal tar was not associated with an increased risk of cancer. [Source]

Psoriasis & atopic dermatitis

• In 2010 the Journal of Drugs in Dermatology published a meta-analysis of 25 studies, 21 of which (84 percent) showed that coal tar was effective in treating psoriasis and atopic dermatitis with limited side effects. [Source]
• In 2013 The Journal of Clinical Investigation published an in vitro study which showed that, in atopic dermatitis patients, coal tar completely restored the expression of major skin barrier proteins which are required for skin cells to mature properly. [Source]