Suitable solvent for tea tree oil on fungal infections and athletes foot

by Brian
(Dorset, UK)

For almost two weeks, I have been treating very long-standing athlete's foot, (with some toenails also infected) as well as very uncomfortable sore and/or itching ongoing rashes spreading from the skin crease between scrotum and each leg with 100% tea tree oil. So far, I think the foot issue is just beginning to come under control, but not yet so for the other infection...the soreness and itching is driving me balmy. Anyway, I believe I should be using a 50% solution on all of my problems areas, and would like to know which solvent would be best to use, and least likely to compromise the fungicidal benefit of the oil.
In addition, I have heard that Manuka oil is even better at destroying fungal infection. Does anyone have any relevant information on this assertion?