Naftalan, located in central Azerbaijan, is home to natural spas and facilities that have curative crude oil. The unique grade of black-brown, thick oil found here is reported to have a composition that has helped patients suffering from rheumatism, arthritis and psoriasis, as well as 67 other illnesses.

Crude oil is found in great quantities in the city of Naftalan, but its properties are noticeably different with naphthalene, a hydrocarbon that is most famously found in mothballs. Making up 50% of the oil's composition, it is said to be beneficial especially in the treatment of dermatological diseases, arthritis, joint pain, urogenital, and cardiovascular ailments. There are significant antiseptic and anti-inflammatory effects of oil, and it has been recommended for peripheral vascular diseases. The oil can stimulate nerve endings, and, as a result, reduce pain relief and speed up the recovery from lesions. It has been used in various forms for treatment including oil baths, massages, and creams.