What Causes Swollen Red Pimples On Face?

Hi, my daughtert (18) has been suffering on and off from what looks like a facial rash but could also maybe be agne. Her face tonight was very severe i.e. swollen, red, a few pimples, and hot to the touch. She has been seeing a dermo. but was told that she just had agne. He gave her some topical meds. that do not work. I think she may have a food allergy to chocolate or dairy. Could this be??