Tsunade truly was an exception. As the strongest medical ninja in the Naruto World, attacks involving toxins and the like were greatly diminished against her, or even completely ineffective.
If it had been a toxin she had never encountered before, it might have had some effect. But after Orochimaru suffered at Yinsen's hands, he still went to seek out Tsunade just as in the original story, hoping that the strongest medical ninja would help him detoxify himself.
Tsunade had indirectly learned about Yinsen's Wood Release. Coupled with the information and intelligence she had received from the Third Hokage, she had long since been on guard.
It looked as though she had caught the rose Yinsen threw with her bare hand, but her hand was actually wrapped in a layer of Chakra that separated her from the flower.
To prevent toxins from seeping into her body through her breath or skin pores, she had also put exceptionally thorough defenses around her body.
Compared to that, Tsunade cared more about the fact that Yinsen seemed not to need hand signs when using Wood Release?
She knew Yinsen possessed the talent for One-Handed Hand Signs, but both his hands had been visible in that instant. A major reason why Itachi's ninjutsu came so suddenly was because his hands were hidden within his wide sleeves, preventing enemies from seeing whether he was forming hand signs. Tsunade was certain Yinsen had not formed any hand signs just now.
"Hand Sign-less Ninjutsu?"
Tsunade was not the only one to notice. Even Jiraiya caught it—if Yinsen could activate his Wood Release without any hand signs at all, then his threat level would rise by another tier.
Just as the two were shocked by this, Yinsen, who had already landed, suddenly vanished.
"This is... the Flying Thunder God