Just spotted a Boots advert on the Gransnet Active page for some mosquito repellent that, it claims, repels "mosquitos that carry malaria and zika viruses". I immediately wondered: fine, but what about the ones that don't carry those diseases? They still bite and cause itching for days.
Besides which, I'm not sure I believe the repellence claim. The only really effective way to keep mosquitos or midges off one is to use a physical barrier like a net. It's the spread of mosquito nets in Africa, for instance, that is reducing the devastation malaria leaves in its wake, not some chemical concoction.