Hello thanks for consulting at hcm.. It is type of allergic reaction that can cause itching of the tongue, lips and mouth. It is called the Oral Allergy syndrome. This syndrome is most often seen in people with a history of hay fever. The symptoms are brought on when someone eats certain foods. Most commonly eating raw fruits or vegetables, especially celery, kiwi, peaches, apricots, apples and nuts, causes the allergy syndrome. Apply topical anesthetics for pain relief,, also give lots of fluids,soups and porridge,, hydrate him well..If fever present control by antipyretic medicines such as crocin etc.. Since bendryl syrup is not helping, how old is your son?? if old enough give him antihistaminics tablets.. please consult a emergency care physician if problem persists.. Hope it helps,,take care..