Around 1 in 5 men and 3 in 4 women have used hair dye.¹ This means that large parts of the population are exposed to the chemicals used in hair dye products.

Due to a strict regulatory framework, the EEA and EU are considered to be the safest market for hair dye products. Nevertheless, approved hair dye products may contain chemicals that can cause adverse effects as there are no good alternatives to these chemicals.

How do hair dyes work?

There are different types of hair dyes based on the chemical composition and how they work.² They can be divided according to how long the hair dye stays in the hair (see Figure 1). In permanent hair dyes, the products contain chemicals that open up the hair strands so that the dye penetrate and are kept inside the hair strands. In this way, the hair dye will last longer than, for example, gloss washing where the dyes only settle on the outside of the hair strands.

What adverse effects can hair dye cause?

Hair dye products can cause a number of different side effects, but allergies are the most frequently reported. The EUs scientific committee has assessed a number of ingredients in hair dyes, 56 of which were defined as sensitisers. A further investigation showed that 13 of these 56 substances were extreme, 23 strong and 10 moderately sensitisers.³

Contact dermatitis 

Allergic contact dermatitis (contact eczema) often occurs after exposure to chemicals. The symptoms are most often eczema, redness, blistering and itching at the edge of the hair, face and neck. These symptoms appear one to two days after hair dyeing. The consumer may also experience swelling, especially on the forehead and around the eyes.

The allergic reaction can persist from around a week to several months after the hair dyeing. Cases of anaphylaxis (an acute and life-threatening reaction) have also been reported.

In several cases of allergic reaction to hair dye, consumers have on previous occasions taken black henna tattoo (temporary tattoo). Henna is a plant extract that gives a faint color that is quickly washed away. Other dyes are therefore mixed in to provide better color properties. One of the dyes that is often added is para-phenylene diamine (PPD) which is an extreme sensitiser. The mixture is then called black henna. If you are going to dye your hair, you should therefore avoid using temporary tattoos in the form of black henna.

Contact urticaria

The symptoms of contact urticaria (hives) can be itching and areas of swelling and redness where the cosmetic product was applied, but also so-called generalised urticaria, where swelling can occur anywhere on the body. The symptoms can occur only a few minutes after exposure to the product and usually disappear relatively quickly (within a few hours).

The chemicals most likely to cause contact urticaria are preservatives and substances added to enhance hair colour, but PPD can also cause such a reaction.

Cancer

It has been claimed that personal use of hair dyes can increase the risk of bladder cancer. However, no such association was found when looking at the results of 17 different studies involving a total of 8500 people with bladder cancer and 14200 healthy controls.⁴  

How to avoid adverse effects

The safest way to avoid adverse effects of hair dyes is to not dye your hair. If you still choose to dye your hair, you should:

• Avoid temporary tattooing with black henna (see above)
• Do not dye your hair if you have a rash (redness, itching, ulceration) after previous dyeing of your hair, eyelashes and eyebrows, or after a black henna tattoo

If you have experienced a rash after dyeing your hair, eyelashes or eyebrows, or after applying black henna, you should see a medical doctor and get an allergy assessment before using hair dye products again.

How is the use of chemicals in hair dye products regulated?

All hair dye products in the European Union must comply with the regulation on cosmetics, which lists around 150 colourants that are allowed to be used in cosmetic products.⁶ It is the duty of manufacturers to ensure that the products they want to sell have undergone a safety assessment before they can be put on the market.

The lack of good alternatives is an important reason why chemicals that can cause sensitisation actually are allowed to be used in hair dye products.

If the hair dye product contains sensitising chemicals, the product must be labelled with a hazard warning with the following text:

• This product can cause severe allergic reactions.
• Read and follow instructions.
• This product is not intended for use on persons under the age of 16.
• Temporary black henna tattoos may increase the risk of allergy.
• Eyelashes shall not be coloured if the consumer:
  • Has a rash on the face or sensitive, irritated and damaged scalp,
  • Has experienced any reaction after colouring hair or eyelashes,
  • Has experienced a reaction to a temporary black henna tattoo in the past.