Since you have a diagnosis of a precancerous lesion I am sure you had a lab test or biopsy.
Clinical inspection is usually adequate for diagnosis, as long as you have seen an internist or dermatologist.
Biopsy must be interpreted along with clinical diagnosis, it is often non specific.
Lichen sclerosis can affect the scalp, and needs intense steroid treatment.
Actinic keratosis needs to be removed.
Clarify the diagnosis with your doctor.
As to your actual questions.
Itching without a rash on the back can be from
hidden cancer [another reason to see your doctor].
Liver or kidney problems
Heavy metal toxicity
Stop treating this yourself.
Talk with your doctor today.
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