If you dreamed that your friend was washing his hair: You should make equal exchanges with each other, it is possible to learn something from someone, most likely about business. To see that your friend is washing his hair in a dream indicates that the troubles of the dreamer will come to an end, his problems will be solved and his mind will be relieved.
This dream is also interpreted as seeing someone else washing one's hair in a dream, and it indicates that the person who sees the dream will not be indifferent to some changes going on around him, and that his attitude towards this situation will give him a contemporary and modern perspective.