*2.3.2 Tar-based actives*

Tars represent one of the first therapies developed in the history of psoriasis [87]. In fact, pine tar has probably been produced in Scandinavia since the Iron Age and its use in medicine was first described by Hippocrates more than 2000 years ago in ancient Greece to treat a range of skin conditions because of its soothing and antiseptic properties [95]. Pine tar should not be confused with coal tar, which has been produced from coal for approximately a 100 years. Today, it is available in various formulations, from gels, to lotions and soap-free bars [96]. As an effective antiinflammatory, antibacterial and antifungal substance, topical pine tar has been used in topical formulations for a long time to relieve itchiness and inflammation associated with a range of dry, itchy, flaky or inflamed skin conditions (**Figure 4**), particularly eczema and psoriasis, with minimal safety risk [96]. Furthermore, both coal tar and wood tars such as birch and beech are also available as topical anti-psoriatic ingredients in different topical formulations [87, 97]. Due to its inherent chemical composition and complexity [98], the mechanism of action of coal tar is not well understood, but it likely suppresses DNA synthesis and reduces keratinocyte proliferation. Coal tar is often used as either a monotherapy or in combination with other management strategies [87, 97]. Pine tar is thought to exert its effect by reducing DNA synthesis and mitotic (cell division) activity, which promotes a return to normal keratin development [96]. Tar-based formulations are indicated for the management of chronic, stable forms of plaque-type psoriasis and scalp psoriasis, whereas their use might be limited in sensitive areas such as around the genitals due to their irritation potential [87].
