depends on the cause, allergy test will you which one likely. either blood or skin patch test. Dust mites, pollen , pet dander is the most common. food allergies, certain chemicals like cleaning sprays or mouthwash ingredients.

if you have allergies around the mouth(chelitis), off brand toothpastes, lip balms are a major cause.

i usually take antihistamines, but i also have atopic dermatitis from dust mites so i have to take topicals.

a uncommon test to take is , testing your IGE levels. <200 is normal, 200-1000+ is sign of allergies. 1000-1999> you are likely to have rhinitis, ashtma or atopic dermatitis, the higher the more severe your symptoms are.

i heard people get allergy shots, but it has mixed results, some reported alleviated thier symptoms, some said no effect, or some said they were temporary.