Cluster headaches are one of the three most common types of headaches (with the other two being tension headaches and migraine headaches), and they cause a wide variety of symptoms. Some of the most common symptoms of cluster headaches include paralysis, tearing, and sweating on one-half of the face only. Some people have cluster headaches regularly while other people may only have one cluster headache before dissipating. Many people who have cluster headaches experience cluster periods where they might experience multiple headaches quickly over a period of a week or a month. Then, the headaches might go into remission, where people do not experience a single headache for a year or more. The most common treatment option for cluster headaches is supplemental oxygen; however, there are other treatment options that are being explored as well, including LSD, psilocybin, and other psychedelic drugs.