Human parasites do zone in on CO2 that we exhale. This was proven in South Africa where veterinary scientists buried "dry ice" (CO2) in the bush and after a short time the area was infested with ticks. Mosquitoes and fleas also locate us with CO2 radar. Parasites migrate to the mouth for water but prefer to feed under cover so the don't normally feed on your face. A German prisoner of war in Australia told me how they had placed the legs of their beds in dishes of paraffin but then they observed the bugs crawl across the ceiling and drop onto the bed!
Here is a product for someone to manufacture. The device would consist of a canister which would slowly emit CO2. This canister could be commercially prepared like butane canisters or be a balloon filled with human breath. The gas comes out of the bottom of a funnel. The insects will follow the gas into the funnel but will not find their way out again.