Is it possible to develop a peanut allergy all of a sudden later in life?

I had a really bad time last night. Around 11:00 PM I was hungry so I ate a snack of 2 ounces of peanuts. I opened up a new jar of peanuts. About 20 minutes later I developed a horrible and painful itching all over my body and extremities. I couldn't stop itching. I couldn't itch fast enough! I never experienced itching like that. It lasted about 50 minutes. Seems like an allergic reaction. But I never had a reaction to peanuts in my life. Is it possible to develop a peanut allergy late in life? Now, I'm afraid to eat peanuts. When I eat peanuts again, I'm going to try just a half ounce and see what happens. Anyway, needless to say, I threw away that jar of peanuts!! Any thoughts?