A few years ago I started to get scabs on my scalp, just like many young men of my age

It gradually got worse to the stage where I frequently drew blood just by combing my hair. The shampoo that I used and had used pretty much since they first marketed it, was Head & Shoulders and looking at the "ingredients" one day saw that it contains 23 chemicals, most with unpronounceable names, but including Hydrochloric Acid.
The next time we went shopping I bought a bottle of Baby Shampoo and after using it for a couple of months I now have a nice smooth scalp (like the proverbial baby's bum)
I also suffer a bit with sinuses, self inflicted by destroying them by smoking for 40 years even though I gave up 15 years ago.
Every morning I woke up with moderately painful blocked sinuses which cleared soon after I got up. Then on one of our trips away I realised that I had clear sinuses when sleeping in a Premier Inn, which pointed to the probability that I am allergic to washing powder/liquid/conditioner and switching to a hypoallergenic one has all but cured that one too.
Probably soap nuts would be even better, but ...
Now all I need to do is find out what's causing my back ache.