The connection between hallucinogens and cluster headache began in 1998 when a Scottish patient posted on a cluster headache website that he missed his fall cycle of cluster headaches and could connect this only with using LSD recreationally. LSD may work because it contains types of ergot, specifically-ergine and isoergine. Psilocybin may work because it is similar to serotonin.
In a study published by Sewell et al in Neurology in 2006 of 53 cluster patients, 21 of whom having chronic cluster headaches, psilocybin completely eliminated attacks in half of these patients. It was not used to treat each headache but rather as a preventative.
Possession of psilocybin mushrooms is illegal everywhere, as it is a schedule I drug, but buying the spores, not the mushrooms, is legal in most states. Several vendors operate online. It is illegal to buy the spores in California, Georgia, and Idaho.
It is impossible to obtain LSD legally. It possible to alter LSD by bromination, which makes it nonhallucinogenic. A 2010 study published in Cephalalgia reported on 5 patients, 4 of whom with chronic cluster headaches, who were administered brominated LSD, did not hallucinate and whose attacks per week, which ranged from 25 to 40, were reduced to almost 0 in all patients.
Dr John Halpern, one of the authors of the original 2006 survey, is trying to bring brominated LSD to market in the United States. For more information, refer to an article by Dr Brian McGeeney, in the journal Headache, 2013.