I get really itchy welts on my chest, forearms, neck and even my head where hair grows. i thought it could be scabies and i've used perthrim cream whi?

Scabies unlikely.: but it is a reason to have things evaluated. Mostly, reaction to a chemical exposure with/without sunlight sensitization effects. Can progress to a second degree burn or infection if the skin breaks open. But, if it is an allergic reaction to a medication, that needs to be fixed. And if it is sensitive skin, (mastocytosis) that needs to be fixed. And theres good treatment for it.