Vitamin c, potentially rancid

I bought a vitamin c serum and when I opened it it had a offish smell, plus it was not sealed properly because there was dried product on the rim, I sent them an email and gave them some time to respond and they haven’t done so. I still went ahead and used it thinking Im paranoid, it gave me a rash ( my skin is used to vitamin c and the other main ingredients) but I had a bad reaction so I didn’t use it again, I was hoping they’d collect it and have it tested as as provide a refund.