I think like you this is either allergy or viral and maybe fungal as a secondary
infection.
Tomatoes are part of nightshades which are notorious for allergies.
Fresh fruit, nuts, vegetables and spices may cause local tissue reactions on the lips, in the mouth and in the throat -Oral Allergy Syndrome.
Foods sulike Bony Fish, Shellfish, Peanuts, Tree-nuts, Tomatoes and Chocolate cause allergies.