Your favorite dandruff shampoo may stop working after a while, and those little flakes may return. Don't blame the shampoo. You simply may have built up a resistance to its active ingredient. To prevent this, try rotating three brands of dandruff shampoo (each with a different formulation), using each for a month. In other words, use one shampoo for a month, then switch to a second brand for a month, then to a third brand for a month, then back to the original shampoo for a month, and so on.