RSO, also commonly referred to as Phoenix Tears, is high concentrated cannabis oil extracted from female cannabis plants that contain at least 20 percent THC or more. Simpson favors high-THC and low-CBD content when treating ailments and diseases. Although the technique Rick Simpson uses to make concentrated cannabis oil is nothing new, he popularized the precise specifications of his oil through activism and patient outreach by sharing his knowledge with anyone who needs it. Eventually, his cannabis oil became known as “Rick Simpson Oil,” or RSO. Simpson believes that in order to treat serious medical illnesses, it’s best to apply the gooey extract to the skin directly or to swallow it. Do not try to dab RSO, as it is made with high-proof solvent and could be adverse to one’s health.