It is mainly withdrawing from cocaine that causes the bug bite thingy, for meth it is usually your mind tricking you and you can even believe you have real bites, you scratch and make it worse. The itching from opiates happen when you are on them, not as withdrawal or long time use, and it rarely feels like bites, more general itchiness.

You can try to moisturise, but if it feels way too bad, treat the itching with anti itch cream. There are different kinds that really help to break the loop, because the more you scratch the more it will itch. Stimulants make things go faster in your body so it dries you out, skin, saliva etc. Plus the mental stress it causes that can even become bug hallucinations.

It is NOT WRONG to treat yourself nicely and try to feel better even if this problem comes from drug use. Treat yourself the best you can and MAKE SURE to really feel proud of any progress you make concerning drug use and general self care.

My uneducated guess this is a problem coming from stimulant drugs. I'm not a drug abuser but I have a love/hate relationship with my Ritalin. I bet you fight with both good and bad with the drugs, cuz there is a reason why people use them. It's hard but not impossible I think, to replace the good from the drug with the good of other activities.

I hope things turn out for the best for you.