Contrary to what the name induces us to think, repellent does not repel insects, at least not as happens with the equal poles of magnets. The substance, in fact, "confuses" the mosquitoes.
Attracted by the various odors naturally exhaled by the skin, the beetles have their "olfactory compass" completely disturbed by the protective cloud of repellent, which is launched into the air by the perspiration of our skin or by the evaporation/sublimation of the devices, and they give up going after anything that is in the middle of this cloud.