My mom put coconut oil all over my cat

I didn't agree to this, she just did it, she hought this would get rid of the fleas. We went to the veterinary and we were told to apply flea treatment, call a exterminator for the house, and use Capstar pills, which I did but she still did this.

His skin got very red and he was very uncomfortable, he did not show any other symptoms of allergy, I bathed him but his fur is still VERY oily, I used a specific shampoo for cats but after scrubbing A LOT I couldn't get rid of all of it (second pic) he was also crying a lot which he never does, and I have bathed him like 5 times already (flea baths last month) so I don't know what to do. He looks more comfortable now but I don't know if it's safe to leave him like this.

I checked him and he doesn't seem to have any more fleas + he is not scrathing. He didn't have any before this.