Allah exempted the sick from having to do Wudu with water and has allowed them to do Tayammum. If Wudu will harm your skin or delay your recovery, then you should do Tayammum, and there is no sin on you.

1. If a sick person cannot (ritually) purify himself with water, by doing Wudu in the case of minor impurity or Ghusl in the case of major impurity, because he is unable to do so, or because he is afraid that it may make the sickness worse or delay his recovery, then he may do Tayammum. 2. The way to do Tayammum following menses is no different from the way of doing Tayammum in the case of minor impurity. 3. It is permissible to offer more than one obligatory prayer with Tayammum and you do not have to repeat it for every prayer.

1. If there is no water in the city, and it is cut off from the houses and mosques, and bringing water from the fire station can only be done with great difficulty and hardship, or the amount of water brought to the fire station is not sufficient for household uses and for purification by doing Wudu and Ghusl, then there is nothing wrong with doing Tayammum. 2. But if water becomes unavailable or cut off, and bringing it from the fire station may cause hardship that is normal for people in such circumstances, then you must bring water for purifying yourselves, and it is not permissible to do Tayammum.

If the shoes cover the foot with the ankles, then it is permissible to wipe over them. But if the shoes do not cover the area that must be washed, then it is not permissible to wipe over the shoes.