Hi Axel,
I had the same problem as you when younger. Check out this link for the mixture I use:
http://forums.deeperblue.net/showthr...ric#post525143
I don't use 90% alcohol, that is too strong and after a while can irritate the ears, and also I only leave the solution in my ears just a couple of seconds, after which I tip my head to clear the solution from the ear. I also do it just after every dive session when I get out of the water. If you do it only "sometimes" after diving and water stays in the ear canals, the flesh gets soft which is what allows bacteria to grow and the infections start.
You might find the boric acid/alcohol solution is easier on the ears than what you were using, but be careful and do check with your doctor. One thing is important, to make sure your ear is completely healed before going back in the water, otherwise you may just start the cycle all over again.
Hope this helps,
Adrian
