They tried to ban DEET — N,N-diethyl-meta-toluamide — in 1991 and 1992, but the chem cos intervened. NYS did ban it, with over 30% product content, since high DEET concentrations were linked to severe skin reactions and neurological problems including seizures.
I’ve known people who would get a rash from DEET, but I haven’t had any problems with it. Mosquitos aren’t bad in southern Arizona anyway, except sometimes during the summer monsoons.
It’s safe to say there is probably no other chemical on earth as thoroughly studied as DEET. If there was a problem with it, they would have found it by now. It was invented in 1946, something like that.
Nothing else comes even close in terms of repelling Mosquitos, and it also lasts several hours. West Nile, Malaria, and probably other diseases linked to Mosquitos are far more debilitating in any case. It does damage plastics, and nylon. But I’m not made of plastic, so I’m good.