No doctor should be prescribing antibiotics for flu, which is of viral origin, not bacterial at all. Any decent doctor, worldwide now, won't prescribe antibiotics when they won't work, because there is a real danger that all antibiotics are becoming useless because of over-prescribing.
Further, if you know you have an allergy to something, it's your duty to tell your doctor, and not to take any medication that you already know will have a detrimental effect on your health.
So, why on earth are you asking us? You are the one with the allergy. Don't take your medication on both of those grounds.