Q: For how long should I keep shampoo on my hair before washing it out?
A: For normal shampoo formulas meant for simple cleansing of the hair, you should be able to apply the shampoo, massage it into a generous lather then rinse it away without a wait. Then you can repeat the process if needed.
Often you’ll notice that heavily soiled or oily hair doesn’t lather as richly as hair that needs less cleansing. Use this as a gauge to whether or not you need to repeat your shampoo process. If your shampoo
lathers up a LOT when you use it the first time, the hair is probably clean. If not, then you can repeat the process until you get a full, rich head of lather.
Now, this is different for medicated shampoos or 2-in-1 shampoos with built-in conditioners. These are often supposed to be left on the hair for some period of time in order for them
to do the additional tasks they perform apart from cleansing the hair. This may be 2-3 minutes in the case of some shampoo-conditioner combos, or can be 3-5 minutes or more with medicated shampoos depending on the formula
and what it’s meant to treat.
Be sure to read your product directions carefully and simply follow them. If there is no specified “leave-in” time listed, then you can be pretty sure that you don’t have to wait before rinsing.