Well, you can tell from the posts below that the Lugol's will stain the nails. So SSKI is tailor-made since it's clear. We happened to get the DMSO from Dr. Wright's Tahoma Clinic Dispensary, but it's probably for sale other places as well. This is for 4 oz, but I noticed they had 16 oz for not many more dollars. Even so, the 4 oz lasts forever. As far as nail strength, his nails have always been able to turn screws, so I don't know how we'd tell :)
They also have a 70% version that's nice if you want to put it straight onto your skin to sooth an ache.
From Dr. Wright --
Fungus under the toenails (“onychomycosis”) is a difficult problem to treat. Even “conventional” anti-fungal drug treatment takes months to work, and (for safety) monthly liver function tests are necessary. SSKI and DMSO rubbed on, around, and under the affected toenails doesn’t work any faster, but it’s just as effective, and definitely safer. Make sure to wear old socks, because SSKI and other forms of iodine leave an orange-brown stain. (Other safe and effective alternatives include geranium oil, oregano oil, and tea tree oil. These and other anti-fungal oils also require “help” from DMSO to penetrate the toenail and soak the fungus underneath.)
Note -- When Dr. Wright says SSKI stains orange-brown, maybe he means their version of it which has saffron extract in it, I'm not sure. Otherwise, clear SSKI doesn't leave a stain, says my husband :)