I can understand your reluctance to use anything. Being sensitive to smells makes it even harder. For your RV, I would purchased a product called Knockout by Verbac. When we got fleas once, the vet's office carried it. You can spray it on any surface inside the RV - after about 1 hr or when dry it is safe for your pet. It works for up to 5 months and works by keeping any fleas from maturing and laying eggs. I would do this as a preventative before you leave on the trip. It worked great when we treated our house. Highly recommend it. No eggs - no new fleas to keep reinfesting him. You can purchase online from Verbac now.