Special stains are dyes that are used for special purpose and are not used routinely in a histopathology laboratory. They are of special interest in research and diagnostic. Most of the special stains are synthetic stains and are composed of harmful chemicals. Continuous and regular exposure to them possesses serious risks to health. Many of the synthetic special stains are found to be genotoxic, mutagenic, immunotoxic and carcinogenic. Their safe handling and disposal is very important from the point of view of health and environmental safety. This review focuses on the effects of the chemical dyes on human health.