Dad lamented that his scalp hurt, and asked Mom and me to find a better shampoo that would be soothing to his head.  Back in the day, when I had hair, I liked Pantene 2-in-1 shampoo and conditioner.  It softened and smoothed my hair and skin.  So, Mom and I brought home a bottle from the grocery store for Dad to try.  Within a few days, he beamed at how much he liked the new shampoo, remarking that his scalp no longer burned or stung.  (I suspect any shampoo-conditioner combo would have worked.)  The following week, at the grocery store, Mom told me to put five bottles in the shopping cart.  Only two sat on the shelf.  But now we know what works, and will add it routinely to the shopping list.