Thnx for the question: you can use Mintop indefinately. It can cause mild side effects like dandruff because it has alcohol as its base. Besides it can sometimes cause irritation and mild headache in some. Overall its safe to use and can be used lifelong if required. since you also have dandruff so you need to use daily shampoo like Nizral 2 % which will not only take care of dandruff but also help hair fall especially if you have associated Androgenetic pattern hair loss. Apply mintop twice daily after shampooing with nizral but first let the hair air-dry after shampooing. try to apply mintop only at the the scalp and avoid it on hairs. plus you can also add Tab. Androanagen once daily after breakfast.