I am a primary care physician in US. I had flat warts on my foot (also called plantar warts) for over a year. I tried topical salicylic acid (17%) and shaving regularly for several months without much success. Eventually, I went to see a podiatrist, who started me on topical Cantharone (Generic name: Cantharidin. It is a blistering agent, derived from the beetle insect.). It clearly caused painful blisters and briefly helped to shrink them. However, that lasted only for a few weeks. What I experienced after was a "donut effect" from Cantharone, where the several hundred tiny wart specks developed around where the initial wart used to be and was subjected to the blistering agent.
That's when I decided to try topical urine therapy. I would soak a gauze in urine, (squeeze and get excess out, just needs to be mildly wet) and put it on the area, leave it on for 8- 10 hours. The next day, I would do some scraping and put a fresh urine soaked gauze. I did this for 2 weeks and as you could see from the pictures, the warts have completely resolved. Absolutely stunning experience! I would highly recommend this to anyone over using the more caustic painful remedies.