The hair does not need to be washed every day, it wears on the hair and especially in the summer when we are out in the sun a lot and swimming. However, it is very individual and depends a lot on your lifestyle and hair type. Generally speaking, it is recommended to wash your hair 2-3 times a week.
People with thin hair are advised to wash their hair about every other day. If, on the other hand, you have thick, voluminous and curly hair, you should wash between every two and every four days.
The water dries out the hair, and the hair is most fragile when it is wet. When you wash your hair and clean the scalp of the natural grease, the sebaceous glands produce even more sebum. If you wash your hair too often, you quickly end up in a vicious circle where you increase the production of sebum.
If you use a sulfate-free shampoo, you don't have to worry about drying out your hair and scalp the way sulfates tend to do.
Hairdressers recommend always using conditioner after shampooing. The conditioner closes the cuticles after the shampoo has opened them, and also helps to protect the hair.