I was not allergic to cephalosporin the other day. What happened to anaphylactic shock today?

This shows that you are allergic. Cephalosporin belongs to the penicillin series, and the mild allergic constitution is fine, but the severe allergic constitution should be paid attention to, because a person's constitution may temporarily have an antiallergic effect after eating a certain food on a certain day, but when the food is digested and excluded from the body, it will return to its original state. This is also the reason why every time people play penicillin series products, doctors will do skin tests. Just because you are not allergic to a skin test doesn't mean you are not allergic.