I has this problem for years. It felt like insects my skin all the time, crawling sensations followed by a nearby itchy "bite". I tried Antibiotics , Sulphur ointments and soaps, and anti- parasite treatments.
The problem ended up being likely a candida infection, and the "fix" for it ended up being a tablespoon of baking soda in a glass of water, twice a day. (It worked amazingly, within 5 minutes.). If you need, you can suppliment this treatment with borax-and-hydrogent peroxide baths. Both did wonders.
I suspect that baking soda works because candida secretes a digestive enzyme that works best in more acid environments and breaks down quickly in more basic environments.
A low_sugar died should also help, since it lowers the amount of excess sugars in the bloodstream, denying the candida yeast some of its food.