Why does Merthiolate sting more than Mercurochrome?

Merthiolate, which contains thimerosal (a Mercury compound), is more irritating to the skin compared to Mercurochrome, primarily due to its formulation and the presence of alcohol. The alcohol in Merthiolate can cause a more intense burning sensation when applied to broken skin, while Mercurochrome is generally less irritating and often has a milder formulation. Additionally, the chemical properties of thimerosal may contribute to a stronger stinging sensation.