When nitric acid touches your skin a yellow spot develops what does the spot mean

Nitric acid is a corrosive acid and leaves the human skin stained yellow due to its reaction with keratin.

Proteins and amino acids that contain phenyl rings form a yellow colored compound when treated with concentrated nitric acid. The yellow stains on the skin are caused due to the reaction of nitric acid with protein keratin present in the skin. This reaction is called xanthoproteic reaction

Answeramino acids;