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Your signs and symptoms are suggestive for exaggerated immune response, possible allergic reaction
, intolerance to any of chocolate ingredients, check out carefully those chocolate that you ate at restaurants and note all ingredients that it contain and in future avoid them and eat only those chocolate that hasn’t mentioned ingredients. You may try antihistamines medicine such Benadryl
I wish you good luck and speedy recovery.
Hope this helps and I have answered your query. If you have additional queries don’t hesitate to ask.