According to the Ayatullah Sistani (h.a) All Alcoholic liquors and beverages which intoxicate a person, are najis and on the basis of recommended precaution everything which is originally liquid and intoxicates a person is Najis.
But all kinds of industrial alcohol used for painting doors, windows, tables, chairs etc. are Pak. ( Mas’ala no 112 & 113)
As long as its medical purpose you may apply but if its non industrial alcohol then it would make the area najis where it has been applied.