Can a guy develop and allergy to you??

TMI warning *

Okay so Ive been with the same guy for almost a year. Weve been able to have sex perfectly fine since the beginning. Recently every time after having sex his penis will be red and spotty. In the spotty parts it basically looks like rug burn and like the skin got rubbed off in some parts but it gets like that no matter how long were going at it even if its just 2 minutes (lol).

Weve both been tested multiple times and have come up negative for everything. He went to his doctor and they put him on like 7 different antibiotics and creams basically treating him for Balanitis or a male version of a yeast infection. I went in a day or 2 after that to my OB and I was negative for any yeast and negative for everything else. I dont have any burning, itching or odor. This coincidentally started after I got the IUD also. We went almost 2 weeks without sex to see if it would heal, it looked almost back to normal and today after sex it basically is right back to square one. If anyone has had anything similar happen or know what it could be please let me know!

Edit: Its Mirena IUD and 10000% lubricated so I dont think its that :(