Sudden Allergic Reaction to Peanut Butter - Need Advice

I suddenly had an allergic reaction to peanut butter twice this week. I thought at first the reaction was to dates (swollen lip, hives, hives the next day) but i ate peanut butter 2 days later (I eat it pretty consistently and have had absolutely no reactions in my whole 45 years) and my lips got tingly, my throat got tight, I got dizzy, and I felt a “rush” in my body.. and then the hives came out again. I waited it out because I was still able to breathe ok, and benedryl cleared the symptoms. I am making an appointment to see the allergist. I am just super confused on how my body one day could eat a certain food with no problem, and the next day could have such a severe reaction. I am nervous to eat so much now. There is not much information on adults suddenly acquiring allergies. I am just wondering if this has happened to anyone else?