Do you think it's allergies? What to apply. Only one red cheek, the se…

Do you think it's allergies? What to apply. Only one red cheek, the second is normal, then redder or paler, the second day, but today lighter than yesterday. There are no such things, by evening there are pimples all over the body, but in the morning they are gone, I think it's pityriasis rosacea because after the street sleeps in warm. But with the cheeks it's unclear.