I sprayed CS on my scalp 2 months ago, and the dandruff is still gone. I assume we need to do a touch up once in a while as required. I will know more in a year after I have 12 months experience with it. For now, it is the best thing I have EVER used for my dandruff. For certain, one application lasts for months.
Here is a new report for CS treating dandruff:
"According to the latest clinical research silver works wonders against the fungal pathogen that causes dandruff – even working better than prescription anti-fungal dandruff drugs...." The rest of the research report here: http://server.publishers-mgmt.com/semk/secm/2016/01/csu/819/more/