make sure that he does not come into some contact irritant , such as a cleaning solution for his kennel or crate. Make sure he does not come into contact with herbicides and pesticides.
In the meantime assume that there may be a fungal problem -- like athletes foot or jock itch . Use one of the "jock itch" creams on the testicles - won't harm , may help. Use coconut oil to sooth .
You may want to use Vetricyn , which covers any fungal , bacterial problem , helps heal the skin and does not burn -- feels like water . Does not dry out the skin.
I had a dog that had been abused . Someone kicked him in the testicles which looked as colourful as a baboons bum, and swollen the size of a large grapefruit . Took to vet to document and make sure the "plumbing" was not damaged . Used coconut oil on that as the dead skin peeled away , the testicle reseeded in size .
just some ideas .