If you use a good quality shampoo, you need not change it often. A good shampoo will ensure that your hair stays in good condition, while maintaining its body and shine. It leaves a coating on the hair after rinsing. This coating protects your hair from the harsh sun and pollution and also prevents your hair from getting dry and frizzy. If you use a cheap shampoo, this waxy coating will stay on your hair and build up with each use. You will find that your shampoo works fine for a few days. Later, your hair seems weighed down and dull, then you know that it is time to change your shampoo.
Sometimes, the quality of water can also affect the way some products react with your hair. You will have to then change your shampoo. You can take the advice of your hairdresser if you are unsure about which the shampoo that will suit you to use.
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