Started any new medications? I react to depakote with itch. And it was an easy change in meds. Or new food?
Benadryl or calamine lotion. ice pack, cool rooms decrease histamines. oatmeal baths by aveeno help soothe.

My oldest can't stand ointment, lotions, or creams at all. I have been having him use the pink, Dove beauty bars and they help his skin heal by adding moisture. He will tolerate soap so I had to find a solution with something he already will use. I tried Dove sensitive skin but the pink works better for him. He will pick still but his skin looks better, anxiety meds decreased his picking but it won't take it completely away. His doctor had me use compression sleeves like football playera wear but he can't stand them, it may help your little guy though, I got his at Academy.

First need to figure out why is he picking his skin? is it eczema? hives? itchiness? Does he have allergies? Or a fungus overgrowth (these are often invisible except under microscope)? Lotion lotion lotion (though make sure to avoid any potential allergens, the ONLY one that works for my boy is aveeno eczema cream). Beware of soaps too, for example my son is allergic to the "pink soap" they use in public restrooms and his skin flakes and he peels and it is just a viscous cycle when it starts. we can only use sensitive skin soaps and even some of those cause him to have reactions. so lots of creams and ointments and treat the underlying condition...and fidgets to redirect him to, you can even try putting tape on fidgets or even paper and have him peel it off instead of picking skin.

Is it finger nails, or skin? If it's nails, they make nail varnish that tastes really, really bad- to discourage nail biting. They might make a similar thing for skin??

My son takes off bandaids too. I use calendula ointment on my son's sores. If it gets really bad, then neosporin with pain relief.