Cat Allergies Treatment

What should I do? I told him I’m willing to bathe the cat, buy allerpet, vacumn like crazy and keep the cat out of the whole upstairs of the house. We had a cat for 3 years who died (she was very old and I had her since I was a teenager but he only lived with her for 3 years with me) and his allergies were not so bad. He had bad days but we dont’ know if that was because of the cat or because of his other allergies.