Easy cure. Apple cider vinegar is great but it is just not strong enough to kill various yeasts (Malazessia spp. [check it out on Google. What you need to do is dissolve 3 teaspoons of borax in half a cup of white vinegar. Pour this over your head (the yeasts begin their life-cycle here), and down onto your face and shoulders (and possibly your chest), and then leave it on for about 20/30 Min's whilst having a bath. Do this for about 3 days running (... If you can), and about once a week for a month. After the vinegar treatment, rinse your head/hair with half a cup of washing soda in a mug of warm water. At the slightest sign of any trouble repeat the treatment. Don't go anywhere near Doctors. Most are just crap at what they do.