Dandruff at teenagers

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To my son of 12,5 years. About half a year back it or he had a dandruff. We tried to use different shampoos from a dandruff, they do not help or assist. On the contrary, apparently, that it or her there is each time all more and more. Many consider or count, is what is it connected with hormonal changes at teenagers. Prompt, please, what agents are the most effective at this age? Thanks.