When Snape gets his leg bitten by Fluffy, he goes to Filch for help.
Snape and Filch were inside, alone. Snape was holding his robes above his knees. One of his legs was bloody and mangled. Filch was handing Snape bandages.
(Harry Potter and the Philosopher's Stone - Chapter 11)
Why would Snape need this? We know that Snape is highly skilled in curing magical wounds, as can be seen regarding Dumbledore's arm.
Had it not been for Professor Snape’s timely action when I returned to Hogwarts, desperately injured, I might not have lived to tell the tale.
(Harry Potter and the Half-Blood Prince - Chapter 23)
Also, of all people to go to, why go to Filch? Filch is a squib.
“He did it, he did it!” Filch spat, his pouchy face purpling. “You saw what he wrote on the wall! He found — in my office — he knows I’m a — I’m a —” Filch’s face worked horribly. “He knows I’m a Squib!” he finished.
(Harry Potter and the Chamber of Secrets - Chapter 9)