Why is histidine associated with cold

Answer 1

Maybe you meant histamine, not histidine. If you really mean histidine, the amino acid, then it would e that histidine is converted to histamine by histidine decarboxylase. And histamine is known to be associated with allergies and inflammation, including the common cold. If you want more detailed information on the role of histamine in these reactions, post an additional question with that in mind.