Reference: Fataawa Ramadhaan – Volume 2, Page 544, Fatwa No.525
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Fatwa No.13595
Question: An imaam of a mosque told me that washing the hair during the day in Ramadhaan breaks the fast, the reason being that water enters through the roots of the hair. What is your answer to this?
Response: Washing the hair during the day in Ramadhaan does not break the fast and nor does water entering through the pores of the hair [on the head]. His (the imaam) statement is wrong, since the Prophet (sal-Allaahu ‘alayhi wa sallam) used to wash his hair whilst fasting.
And with Allaah lies all the success, and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.