DMSO and tea tree oil
(US)
I mixed 1 part DMSO (bought from my local feed store) and 1 part tea tree oil. Applied a drop to the top of the nail once/twice a day and it worked. The DMSO is a penetrant, and it takes the tea tree oil with it.
http://en.wikipedia.org/wiki/Dimethyl_sulfoxide
http://en.wikipedia.org/wiki/Tea_tree_oil
Yes, tea tree oil has been used for years on fungus nails and certainly using DMSO as the penetrating agent should in theory allow the tea tree oil to reach the fungus.
Marc Mitnick DPM