Ever enjoyed a juicy mango, a ripe tomato or a crisp apple, only to notice redness and swelling around your mouth and face? You're probably experiencing a mild reaction to proteins in some fruits and vegetables (as well as some tree nuts), known as oral allergy syndrome. Chances are you suffer from seasonal allergies too, since these proteins are known to resemble pollen [source: Children's Hospital of Pennsylvania].
For more severe reactions, pop an antihistamine and avoid the food in the future. But if you're not yet ready to give it up entirely, try cooking it, which alters the offending proteins, or removing its peel, which contains the highest concentration of allergens [source: Landau].
In some cases, food reactions that cause rashes on your face and body indicate a severe allergy, particularly if you experience other symptoms such as nausea, vomiting, diarrhea, lightheadedness, nasal congestion, shortness of breath and difficulty swallowing. Among older children and adults, the most common culprits include fish, peanuts, shellfish and tree nuts [source: HealthCentral].
If you think you might have a food allergy, get to a doctor for comprehensive allergy testing. Although it's rare, severe reactions can be fatal, so you'll need to avoid the trigger and possibly carry an epinephrine injection in case of accidental ingestion [source: WebMD].