Keep in mind that some ingredients in hair products are only safe to leave-on in given concentrations and if left on for too long could damage your hair or scalp.
This is not a bad thing – conditioners are also rinse-off products for the same reason. In some of my pre-shampoo detangler recipes for instance, I include a lot of glycerin for extra moisture and softening but if they were applied as leave-on products your hair could get very dry. You don't want to leave a high concentration on glycerin on your hair
A leave-on detangler on the other hand can be safely applied and left on hair without any adverse effects.
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