Vegetarian food, inhalants, drugs, and non-vegetarian food can all cause allergic reactions. You can get tested for allergies to these items with a blood test.

Allergy tests
Vegetarian food allergy test: Checks for antibodies that trigger allergic reactions to vegetarian foods
Non-vegetarian food intolerance test: Checks for intolerances to non-vegetarian foods
Drug allergy test: Checks for allergies to medications
Inhalant allergy test: Checks for allergies to inhalants like dust, pollen, and danders
Food allergy test: Checks for allergies to specific foods, including potential life-threatening reactions
Food plus drug allergy panel: Checks for allergies to specific foods and drugs

Symptoms of food allergies
Itching in the mouth
Swelling in the face, lips, and mouth
Abdominal cramps and diarrhea
Vomiting and nausea
Difficulty breathing
Wheezing and asthma-like symptoms
Hives or eczema on the skin
Stiffness in the throat muscles and inability to swallow