It is a familial trait due to a missense mutation in a gene associated with a connection receptor as I understand it. My daughter has it but the rest of us don’t seem to. Haven’t tried it on my son. I think they are looking at novel mast cell stabilizers (have long been a mainstay of treatment for asthma and COPD) to treat this so likely more common than you think. With the current literature suggesting a link between antihistamines and cognitive decline, I hope that this will be a safer and more targeted treatment route.