Coal-tar dyes in cosmetics refer to a group of synthetic colourants derived from coal tar, a byproduct of coal processing. These dyes are commonly used in cosmetics to add vibrant and long-lasting colours to various products such as lipsticks, eyeshadows, and hair dyes.

Advantages:
Firstly, they provide vibrant and long-lasting colours, allowing cosmetic products to create visually appealing effects. These dyes are highly stable and resistant to fading, ensuring that the colours remain vibrant even after prolonged use. Additionally, coal-tar dyes are versatile and can be easily blended to create a wide range of shades, giving cosmetic manufacturers the flexibility to meet various consumer preferences. Moreover, these dyes are cost-effective, making them a popular choice for cosmetic formulations.

Disadvantages:
These dyes are derived from coal tar, which is a byproduct of coal processing and contains potentially harmful substances such as benzene and toluene. These chemicals have been linked to various health issues, including skin irritation, allergies, and even cancer. Secondly, coal-tar dyes are known to have poor stability, meaning they can easily fade or change color when exposed to light or other external factors. This can result in the product losing its desired appearance over time. Lastly, the use of coal-tar dyes in cosmetics raises environmental concerns as the production and disposal of these dyes can contribute to water and soil pollution.

Conclusion:
The presence of these dyes in cosmetic products poses potential risks to human health. Studies have shown that coal-tar dyes may have carcinogenic properties and can cause skin irritation and allergic reactions in some individuals.

References:
http://thetoxicfreefoundation.com/database/ingredient/coal-tar-dyes#:~:text=Coal%20tar%20dyes%20are%20artificial,liquid%20of%20extremely%20high%20viscosity.
https://www.sciencedirect.com/topics/chemistry/coal-tar-dye