Approximately 5 per cent of people who use permanent hair dyes develop some sort of an allergy to the dye, according to Jan Modric of Healthhype.com. Allergies include contact dermatitis, redness and itching of the skin that has been exposed to the hair dye. A number of substances in hair dyes can cause allergic reactions but the most common is 4-ParaPhenyleneDiamine (PPD). When the PPD reacts with peroxide is when an allergic reaction can occur. Before using any type of hair dye it is important to first test for hair dye allergies. The allergy test is called a "patch test;" it can be administered right in your own home.
Determine which type and colour of hair dye you are going to use. Open the package and pour a few drops of the colour into a small bowl. Add equal drops of the developer to the bowl and mix with a tooth pick.
Dunk a cotton ball or Q-tip into the hair dye solution. Apply a quarter-sized dab to the inside of the elbow.
Cover the hair dye solution with a Band-Aid so that it does not rub off on clothing. Remove the Band-Aid after 30 minutes but do not wash off the hair dye solution.
Closely monitor the skin, where the hair dye was applied, for 48 hours. If you see any signs of redness or if the skin starts to itch you are more than likely allergic to some of the ingredients in the hair dye. If a reaction occurs, rinse the skin immediately with warm soapy water to cleanse the area affected by the hair dye. Discontinue the use of that particular hair dye and try a different one.
When making a hair colouring appointment with a hairdresser have the hairdresser do a patch test 48 hours before the appointment to ensure that no allergic reactions occur.