Can you get an oral allergy even if you haven't eaten anything? my mouth is itchy and i have a rash. i have also been severely stressed lately so maybe its that?

You will be your best detective. Think what goes into your mouth. Toothpaste/mouthwash/fingers/drinks/inhaled air contaminated with germs/etc. Sometimes the mouth reacts to simple environmental germs with an outbreak & you may not realize you were exposed.

There are many possible causes, including a localized dermatitis. Food allergies may cause rash,itching but are often associated with hives and GI upset