A.A.
Take or leave this advice...I haven't tried it yet myself for my 3 year old who bites her fingernails. But my husband keeps telling me to try this. This is what his mom did for both him and his sister when they were young. She combined cayenne pepper and some clear nail polish and put it on their nails. Ouch when they tasted it! I haven't had the heart yet, but he said it worked quickly so maybe I should. Just thought I'd share.... :)