A diminutive sample of blood is extracted and tested. It measures the precentage of IgE (immunoglobulin E) present, a major factor in virtually all allergies. The results are accurate in slightly over two-thirds of allergy cases. Measuring the size of IgE present gives a good prediction for those who may be allergic, nonetheless it is only a probable result. It doesn't actually measure allergy directly in view of the fact that skin tests do. "Eczema, hives and other skin conditions are a common reaction in those who have a type of allergy called contact dermatitis. It may be caused by sensitivity to hair dyes or perfumes. It can result from wearing rings formulated from certain metals like nickel or gold."