Why would you're face swell up other than having a food allergy?

If you mean swell up as in zits or pimples, that's acne. If you mean larger swelling, it's likely an infection of some sort. Check to see if the skin where it is swollen feels hot. If it does, see your doctor for some antibiotics. If the swelling is around your jaws, it's probably an infected tooth and you need to see the dentist quickly.