I recently broke out with many canker sores.
I suspected thrush. Dad has thrush and I have been spending much time with him. A quick internet review suggested that thrush is rare in middle-aged, healthy men but that stress predisposes one to getting it.
The same quick review revealed that there are many biocides and fungicides that are effective on thrush, a yeast infection of the mouth. Unfortunately, they require prescriptions.
There were also many "folk" remedies suggested; remedies like gargling with Greek yogurt or rinsing out my mouth with brine strong enough to float a potato 8 times a day.
On a whim, I researched other, non-prescription sources of the modern biocides.
This is what I found
$36 to make 40 gallons of 0.12% solution similar to the prescription mouthwash Peridex which sells for $9 a pint.
Of course, it is a Federal crime to use the product in off-label applications. That is where my glorious plan hit the rocks of reality.
I could not find a volunteer who agreed to supply the applicators listed on the label.