I am having an allergic reaction to salmon, should i take benadryl?

If mild hives or...: If a food reaction is merely itching, nausea, or some hives, a person can take antihistamines (like Benadryl) to decrease the reaction. Hives are due to release of histamine, commonly related to allergy to foods, medicines, viruses, molds, animals, pollens, etc... Some people release histamine and get hives when exposed to cold temperatures, cold water, sunshine, stressful situations, etc...