My oldest Crohnie has Remicade induced psoriasis. She has it in her scalp, ears, neck, chest, back and genitals.
She mostly has plaque psoriasis but in the genitals it is usually inverse psoriasis.
What you are describing could be pustular psoriasis. Not usually in the genitals but it certainly could be. O has gotten it on her back, stomach and chest before.
She is a swimmer and with all her broken skin from the plaques the term did tell her to shower as soon as she got out of the germ infested pool. The reason being the broken skin combined with the immunosuppressants and the higher likelihood of infection. She has actually never heeded the advice or gotten an infection...just lucky I guess but I wish she would shower right after practice.
Here is a link to the NPF. I think you could find pictures there and see if what he has looks like pustular psoriasis.
https://www.psoriasis.org/about-psoriasis
Either way you will need to see a derm as the term will help you treat the psoriasis.
There isn't much you could do about it. We have added methotrexate to treat the psoriasis and it lessened it a bit but not enough to justify the side effects or added drug burden. She just uses steroid creams. Two weeks on, two weeks off. We have also tried decreasing her Remicade dose a bit to see if that helped but the only thing that did was send her into a Crohn's flare. So she just lives with it. She would rather be an itchy, scaley mess than deal with Crohn's.