I am seeking medical advice for my 4.7-year-old child, who has been suffering from chronic urticaria for 16 days. The symptoms began with fever and cold, followed by the appearance of reddish patches the next day. This is the second instance, with the first occurring last December. Which specialist should I consult - a dermatologist or an allergist? Are there any diagnostic lab tests available to identify the underlying cause of urticaria?