Most people choose shampoo by what they want their hair to look like. If your scalp is the problem, choose for the scalp instead – hair will look after itself far better once the skin underneath is comfortable.
These are formulated with that in mind. The duo pack is the sensible buy, since a matched conditioner avoids undoing the shampoo's work with something harsher.
Work the shampoo into the scalp rather than piling it on the lengths, and rinse thoroughly – residue left behind is a common irritant and people rarely suspect it.
Cooler water helps more than most products do. Very hot water strips the scalp and leaves it producing more oil, which is the opposite of what anyone wants.
Scalps take a few weeks to settle after any change of product, so switching every fortnight guarantees you will never know what works. Stay with something for a month.
If your scalp is sore, broken, flaking heavily or not settling, that is worth showing to a pharmacist or GP rather than working through more bottles.
FAQ
Should I choose shampoo for my hair or my scalp?
The scalp, if that is where the problem is. Hair generally behaves once the skin underneath is comfortable.
How long should I give it?
About a month. Scalps take a few weeks to settle after a change.
Does rinsing matter?
A great deal. Residue left in is a common irritant and rarely suspected.
When should I see someone?
If your scalp is sore, broken, flaking heavily or simply not settling.