Quote Originally Posted by Buffalobiian View Post
Her testing poisons and stuff on her forearm is played off lightly in this show. Some wounds just never heal and become infected/rotten.
The anime is a bit less graphic when it comes to Maomao's testing arm. It shows it more as pink scar tissue when in the manga, it is usually depicted with some ravaged post-festering areas and burn marks that have scarred very badly.

There is ample reason why Gyokuyou's ladies-in-waiting believe that Maomao was severely abused.