If i have kidney disease , and i have a very dry scalp, can i use apple cider vinegar, to help me ?

Questionable benefit: I am not certain that the vinegar will be of any benefit. Your tolerance for the vinegar will depend on you renal clearance.

Sure: If your kidney disease upsets your stomach, the vinegar may make it worse. If you're expecting drinking the vinegar to help dry scalp, you're overly optimistic. Applying it topically might help -- your physician may have other suggestions. Apple cider vinegar is promoted as being good for everything, which itself should let you draw a reasonable conclusion. Still, it's interesting.