Take another look at the original sentence:
You wanted to fix it this way:
To delete the comma between cats and he would cause an equally bad problem, a fused sentence. A fused sentence occurs when you have two main clauses joined with no punctuation whatsoever. Ryan is highly allergic to cats is the first main clause. He requires at least twenty god-bless-yous is the second main clause. The spot between cats and he needs a stronger break than blank space.
You might want to consult the rules for fixing comma splices and fused sentences.