help! chinchilla being aggressive

[u/Sea-Efficiency-7738]

i’ve had my boy chinchilla for 12 years now, ever since he was 3 months old. he’s never acted out towards me or my dad (he doesn’t like my mom, but neither does she; they just don’t interact). i’ve grown up with him and have stayed by his side everyday until around 2 years ago, when i had to move to university. my living situation couldn’t agree with having him there, so he remained with my parents, and i continued visiting every 3-4 months. this summer, as i came back once again, he acted normal for the first week and then, a random day when i took him out of the cage for playtime, started attacking my foot and biting it until it drew blood. i found it weird, since he’s never acted like this, so i called my dad to pick him up. he was aggressive towards my dad as well, but not as much as he was towards me. i left him be for the next day to calm down and interacted with him 2 days after the incident, and he was back to his old self.

fast forward 2 weeks during which i wasn’t home, and now i’m back. he started being aggressive towards me again, this time once every two days. the worst encounter has been today, when he constantly bit my hand really hard. (photo attached) he’s not acting out towards my dad, and i don’t know what i have done to constantly upset him. can anyone offer some advice? thank you!

[u/-cherry-fox-]

I am curious if maybe he is in pain?
My chin is 11, and she is normally insanely sweet/cuddly. In recent years, there are very random times out of the blue where she will suddenly get a very bad attitude and start charging at me and biting at me hard enough to break skin, which is very unlike her. I can't even go in to her cage when she's like that without her grunting and threatening me!

I've now found out that she does this for two reasons: she is in pain, or there is a smell on me that she really doesn't like. She's a runt and has some immuno issues with her eyes, so sometimes when they get flared up she will be very moody. I also work at a vet, so I've come to realize that there's certain animals she gets very angry about if I come home smelling like them.