Betel nut oil is an oil that is extracted from the seeds of the areca palm tree, which is also known as the betel nut tree. It is typically used in traditional medicine and is not commonly used in modern skincare or culinary applications. Betel nut oil is known to have a variety of medicinal properties, including anti-inflammatory and analgesic (pain-relieving) effects. It is also used to treat skin diseases, wounds, and other conditions. However, it is important to note that betel nut is a stimulant and can have addictive properties when chewed or consumed in large amounts. It is also known to have some negative health effects such as oral cancer, so it should be used with caution. Therefore, it's important to consult with a healthcare professional before using betel nut oil.