Hotspot on my cat

Hello all,

I have a four year old American short hair cat. His name is Axel. A year or so ago I gave me a flea and tick treatment and it causes bald spots all over due to the irritation. I took him to the vet and they gave him a steroid shot and it helped for months. He now has hot spots on his leg, I took him to the vet when I saw them and they gave him antibiotics and anti-inflammatory shots. The did nothing and the only thing they recommended was an allergy test…anyone have any other solutions, I have him in a cone and have been giving him auntie itch cream.