If mayonnaise could consistently kill lice, why would there be any lice products, prescriptions, and lice removal businesses?
Think carefully before you attempt this home remedy. Every article that recommends mayo also recommends combing with a lice comb because lice combing gets rid of lice. Mayo may suffocate some of them, but you won’t get the nits and probably won’t get all the adults. When lice can hold their breath when submerged in water for more than 8 hours, mayo is not going to do much.