If all your blood tests results are normal,i should say its good thing.Some people have special body type,they response abnormally to the ordinary things which normally other people do not response.Their are list of these things probably u could also go for patch test for determining these things.Some people are allergic to alcohal,sea food,dust mite even hot spicy food.I would also like to suggest u not eat food like fish,eggs and foods which are easy to cause allergy for sometime including alcohal. U can also go for urea breath test used to identify infections by Helicobacter pylori in gastritis which can also cause pruriitus .Also try to review drugs taken within three week which be cause of your present condition.