For this reason, prior to any tint application it is very important to do a skin test before every application, because an allergic reaction may occur even though you may have coloured your hair for many years without any problem

A skin test is quick and simple to carry out. A small amount of tint and developer (the size of a pea) are mixed and dabbed behind the ear or elbow using cotton wool. Ensure you immediately seal the bottles after pouring your pea sized measures. The test should remain 48 hours, initially it is common to feel tingling or slight irritation from the tint and the skin may redden subtly. However, these sensations should disappear within a maximum of 60 minutes. If, once applied the test causes severe burning, itching and or begins to inflame rinse the skin immediately with cool water. In addition, if the skin is still reacting after several hours and appears patchy, a reaction has happened. People may initially find the skin shows no response to the tint. However 12 hours after initial application it may suddenly become inflamed and swollen. In this case you are very likely to be allergic to tint, and a scalp application must not be carried out.