Physical urticaria tests are used to identify the triggers of the so called physical urticaria. There are several types of physical urticaria, triggered by various stimuli, like heat, cold, pressure, vibration, solar light, or contact with water. Depending on the suspected offending cause the test will be also varied.
Dermographism: a blunt object is used to “write” on the skin.
Heat: the body temperature must be raised making exercise or through immersion in hot water.
Cold: usually contact with an ice cube will be used. Also immersion in cold water, or an instrument to apply different temperatures in the arm are used.
Pressure or vibration; instruments are used to apply pressure or vibration in the arm.
Light: a lamp with different wavelengths is used to apply light on the skin.
Water: contact with water at different temperatures.After the stimulus is applied, the patient is watched to see if hives or oedema (inflammation) of the skin appears.
Antihistamines change the results of the test, and should be withdrawn 4-7 days before. If you are scheduled for a physical urticaria test you should ask your doctor.