Going to allergist to be checked for enviremental allergies and to cats/dogs, what do they do? how long does it last? what should i bring

Usually skin testing: With skin testing the allergist usually pricks the skin with a small amount of the material you may be allergic to. A positive test is a hive. Sometimes the allergist will also test by injection a very small amount of the potential allergic material in the skin, .One must be off antihistamines for 3 days or more. Blood tests can be done if one can't do skin tests. Often, it takes 1-3 hours