5-Hydroxytryptophan (5-HTP) is a precursor to serotonin that may help modulate neurotransmitter pathways involved in cluster headache pathogenesis. By crossing the blood-brain barrier and increasing serotonin synthesis, 5-HTP can potentially reduce neurogenic inflammation and alter pain perception, though its efficacy for cluster headaches is not definitively established. Some clinical evidence suggests it may help reduce headache frequency and intensity by influencing central nervous system serotonergic mechanisms.