For the ghusl of janabah, is it obligatory to pour water over head? The questioner is suffering from illness due to untimely bathing.
Its waajib that water reaches the entire body for ghusl of janabah as for The one who fears for himself sickness or harm it is allowed to do tayammum
لا تقتلوا اننفسكم ان الله كان بكم رحيما
Do not kill yourselves Allah is ever merciful to you all
لا ضرر و لا ضرار
Tayammum by wiping over the face and forearms with turaab Also it has been mentioned that Amr ibnu Al Aas woke up on a cold night in state of janabah recited the above aayah and made tayammum
See bukhari chapter (no. 145)