The Cold Virus and Tayammum

Question :

I am suffering from a continuous cold, and medication has not helped me, so can I make Tayammum? And what is the ruling in cases of Janabah?

Answer:

If a person is ill, and using water would harm him by worsening the illness, or delaying the recovery, then it is allowed for him to perform Tayammum, based upon the Words of Allah, the Most High:
But if you are ill or on a journey or any of you comes from answering the call of nature, or you have been in contact with women (i.e. sexual intercourse), and you find no water, then perform Tayammum with clean earth and rub therewith your faces and hands.

But it would appear that this continuous cold of which you are complaining will not be made worse by water, nor will your recovery be delayed, even though it is continuous. Since it is clear that using water will not harm you, then you must clean yourself with water by making Wudhu' for minor impurity and Ghusl for major impurity, because it appears (based on what you have said) that your Tayammum will not benefit you at all. And you must present yourself to the doctor with regard to this matter, then if it is confirmed that using water will harm you, there is no objection to you making Tayammum. If this is not the case, then you must cleanse yourself with water.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 2 Pages 94