Try to eliminate all the mechanical problems that can cause that 2nd degree burn you are referring to.
1. short must be tight, so the testicles stay only in one position and that is on front of the pubis and all up.
2. if you do not use bibs get a pair of suspenders and be sure they are tight on your shoulders. If they do the trick buy a good bibs like the santini carbon.
3. saddle should be flat, and the ischion bones should be where the wide part of the saddle is. If you have a tendency to slide forward it means the setback is too much, so move the saddle forward or buy a seatpost with 0 setback.
4. Do not use any cream. Creams where made for the all leather chamois to make it soft. They also help if the problem is on your butt to decrease friction but that is not the case with your testicles.
5. If you do not have a problem except when you ride this is not a mycosis and most likely not an allergic reaction.
6. If you have a lot of pubic hair, trim it a little bit, but this should not be a major problem if the short is tight.
7. Do not blame too much sex on cycling