This will make your skin crawl. New research shows that lice in at least 25 U.S. states are growing immune to over-the-counter treatments. More than 100 samples from 30 states showed that a majority of lice carry genes — thanks to a trio of mutations — that help them resist readily available insecticides called pyrethroids. Lice aren’t known to transmit diseases, but victims are usually itching to banish them. And experts say those plagued by the most headstrong of these lousy pests should turn to prescription-based solutions.