many people are allergic to the resins etc in live evergreen trees....in my experience the allergic reaction has been stuffy nose etc....could easily be your problem....however allergic reactions of the skin, usually require actual contact with the allergen....could be hives, but hives don't usually develop blisters on the top...they're generally just itchy red bumps....i would check in with your regular doc....sounds like a mild case of chicken pox to me....
chicken pox:
Symptoms
Symptoms of chickenpox begin between 10 and 21 days after a person is exposed. The illness typically includes fever and a generally sick feeling. This is soon followed by itchy, red bumps that quickly become fluid-filled and are easily recognized as chickenpox. These skin blisters are round, about 5 millimeters to 10 millimeters across (about the size of a pencil eraser), with a red base. Sometimes, they are described as a "dew drop on a rose petal." They appear in various stages over the next few days and eventually crust over. These blisters may appear anywhere there is skin, even inside the mouth, throat or vagina. Some patients have only 50 blisters or fewer. Others have too many to count.
Diagnosis
If you or someone in your household develop a skin rash, see your doctor. He or she may suspect chickenpox over the phone, especially if that person has not had the chickenpox vaccine or the chickenpox disease before, but it is important for the doctor to look at the skin rash. It also will help to know whether the patient has been exposed to someone with chickenpox, although this is not necessary to make the diagnosis. Special blood tests, such as the FAMA test (fluorescent antibody to membrane antigen) and the ELISA (enzyme-linked immunosorbent assay), are also available, but they do not need to be done in most patients. Sometimes your physician may scrape a chickenpox blister to examine under the microscope.
Expected Duration
Chickenpox blisters form over a period of 3 to 5 days and then crust over during the next 7 to 10 days.