Selection Criteria and sample size calculation 78 subjects who come to Allergy Centre for treatment of idiopathic urticaria, with or without angioedema and pruritus (U/A/P), will be randomized into two parallel groups; treatment group (TG) will be asked to follow a histamine-restricted diet for 4 weeks and the control group (CG) will be asked to follow a well-balanced diet instructed by a dietitian for 4 weeks. A well-balanced diet for the CG subject is tailor-made by the dietitian according to subject's usual intake to ensure that the subject's energy requirement is met and all food groups are consumed. Subjects in both groups are also instructed to have adequate water intake during the study period. Both groups are asked to record food diary and symptoms during the study period. Consent form will state that it is a study to compare the efficacy of both diets. After the study period, subjects in the CG will be able to follow a low histamine diet if this is proven to be beneficial, so everyone will have the potential to benefit from the low histamine diet and vice versa for the TG subjects.