As much as one wishes for a low/non-toxic alternative and as much as various people try to make you believe that there are natural non-toxic alternatives, high-strength DEET (by brand, Muskol, J&J's Off!) is the only proven repellent that lasts for any length of time.
Scientists who study mosquito know it works but no one is exactly sure how it works.
Below is an interesting article about how mosquitos find a host (multiple ways, at least heat, CO2, scent, shape).
https://www.theatlantic.com/science/...ellent/423672/