Hair shedding of up to 20-80 strands per day is normal (non-wash day, up to 140 on a wash day).
This represents the hair follicles in the post telogen stage that are ready to transition into new growing hair. For ANY shampoo to have therapeutic/medicinal effect on hair loss, it has to be left on the scalp for at least 10 minutes for any meaningful absorption.
But also, one has to use ‘the shampoo’ twice a day on a continuous basis. This is not practical at all; hence it is unlikely that such shampoos have any substantial effect on excessive hair loss. It is better to use a shampoo that is appropriate for the type of scalp and hair and to wash the scalp 2-3 times a week and carry out good hair care habits.
Not shampooing regularly increases the natural oils on the scalp which may increase the growth of yeast making certain scalp contains like seborrheic dermatitis manifest or get worse.
One will notice that sulphate free shampoos (SLS free) lather less. Sulphate based shampoos are more drying to the hair which is a problem for people who have colour dyed or relaxed hair as it makes the cuticle dry and prone to ‘lifting’. For some people, it can cause irritation and exacerbate eczema. But on the whole, people who use ‘SLS’ free shampoos will not get better hair care.
Choice of shampoos is a personal choice and people learn quickly their preferred shampooing frequency and choice.