South Carolina Cosmetology Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

The skin test is a crucial step before administering a permanent hair color service. This type of color service involves the use of stronger chemicals that create a more long-lasting change to the hair color. Since permanent hair color can cause allergic reactions in some individuals due to the ingredients, particularly para-phenylenediamine (PPD), performing a skin test, also known as a patch test, is vital. This test usually involves applying a small amount of the hair dye to a discreet area of the skin, typically behind the ear or on the inner elbow, and observing for any allergic reactions over a 24-48 hour period.

Other services, such as highlights, do not typically require a skin test because they often use lighter solutions that are less likely to cause a severe allergic reaction. A shampoo and set is a styling service that does not involve any color change, thus eliminating the need for a skin test. Similarly, a glaze, which usually adds shine and slight tonal changes to the hair without lifting the natural color, generally involves milder products that do not necessitate the same safety precautions as a permanent color service.