Are the substances such as medicine applied on skin for treatment obstacles to perform minor ablution?
If washing the substances such as ointment, etc. that are applied for treatment to an organ to be washed in ablution but form a layer on skin does not harm the treatment, these organs should be washed. If washing gives harm to them, one should wipe over them with wet hand. If wiping is also harmful, one should not perform it (Ibn Abidin, Radd al-Muhtar, I, 217, 472).
If these substances do not form a layer on skin, they do nor affect the validity of ablution.
Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS