But as near as the medical world can tell, itching is caused when the body releases chemicals called histamines as a reaction, for instance, to proteins injected into the skin by biting insects. Scratching to relieve the itch, then, causes cells to release more histamines. That, in turn, leads to more itching. Pennisi believes scratching offers the immediate sensation of relief because it's inflicting pain on the region. But once the distracting pain subsides, the itch returns.
Some products use a local anesthetic, which numbs the bite or rash.
For instance, the active ingredient in Lanacane is benzocaine. Other creams use hydrocortisone, which reduces inflammation. Hauser is most enthusiastic about a brand-new product called IvyBlock, the first prevention product with ingredients approved by the Food and Drug Administration. It's a barrier lotion that bonds with your skin, preventing the urushiol from bonding with your skin. It's best, of course, if you can spare yourself the itch grief in the first place.