allergies are not something we are born with but rather a sensitivity that is acquired over time from repeated exposure. there is really no logical reason why you developed a sensitivity to ibuprofen but you did. you will need to avoid this drug and drugs in this class from now on (assuming it was a true allergic reaction).
what causes a person to become allergic to ibuprofen? . i have used ibuprofen for years with no problems. i was started on meloxicam and had an allergic reaction to it. i took ibuprofen after this and had a reaction to it also.