What allergens outside could make me suddenly itchy-mostly on my face, head, & ears? i have not made changes to any products i use. i am in ca.

Plants: You may have an allergy to certain grasses or trees. Get an allergy test from your doctor

Contact allergy: If this occurs only on area above the neck, I would suspect a contact allergens used on the face and scalp. Hair products would be on my number 1 list. In contact allergy, the skin does not start to rash until 24-72 hrs after the application. Avoidance is the key but may try topical hydrocortisone cream for the time being.