Hair dyes

How are hair dyes labelled?

Permanent and semi-permanent hair dyes, which use coal tar dye bases and intermediates to produce the colour, must by law also carry on their labels:

• a warning that the product may cause skin irritation on certain individuals
• a warning not to use the product for dyeing eyebrows and eyelashes because this may cause blindness
• instructions for carrying out a preliminary test for skin irritation, called the patch test

What is the patch test?

The patch test is a way of seeing how sensitive you are to certain products, including cosmetics.

To do the test, wash a small area of the skin behind your ear or on your inner forearm, then apply a small amount of the cosmetic and let it dry. After 24 hours, wash the area gently with soap and water.

If there is any redness, burning, itching, blistering or irritation, stop using the cosmetic.

Be sure to use the patch test whenever you use permanent or semi-permanent hair dyes. Sensitivity to these ingredients may not show up until you have used these products a number of times, so repeat the patch test before each use.