Seven hundred years ago, Marco Polo mentioned "a big well with oil . . . that cures dermatoses and other diseases" located in today's Azerbaijan.1 To date, Ivanic Grad, near Zagreb, Croatia, is the only other location in the world where this heavy naphthen oil referred to as Naphthalan (Industria Nafte, Zagreb, Croatia) is found and successfully used in the treatment of psoriasis.2 Naphthen oil contains polycyclic naphthol hydrocarbons and to a lesser degree bicyclic to pentacyclic hydrocarbons, most importantly those with a cyclopentanoperhydrophenentren nucleus.
Thaci D, Schindewolf M, Smeh-Skrbin A, Krnjevic-Pezic G, Vrzogic P, Dobric I, Kaufmann R, Boehncke W. Heavy Naphthen Oil Exhibits Antipsoriatic Efficacy In Vivo and Antiproliferative as Well as Differentiation-Inducing Effects on Keratinocytes In Vitro. Arch Dermatol. 2000;136(5):678-679. doi: