Each subject will complete a food diary, in addition to the symptom score chart, where he/she will record his/her dietary intake for each snack and meal during the 4-week study period. The food diary will be evaluated by the Allergy Centre dietitians for adherence to the diet. Diet compliance score (DCS) is scored as 0 = not comply at all; 1 = poor diet compliance (intake of 2 or more high histamine foods daily); 2 = good compliance (intake of 1 or less high histamine food daily); 3 = excellent diet compliance (intake of 3 or less high histamine food per week).