From what I can tell, itchy nipples in men is a hormonal thing.
I'm a guy and I've experienced this occasionally over the last few years. Never noticed a cause and effect until recently. After upping my daily intake of lecithin (after reading more about its health benefits) I experienced this itchy nipple thing, so I backed way off the amount and the itching stopped. This lecithin is made from soy which is known to be high in phyto-estrogens, etc. I don't think a guy w/ a healthy liver would experience this. Someone like myself w/ an impaired liver, or congested, sluggish or whatever I have--the conjugating and converting doesn't happen like it should. I'm also much more sensitive to breathing in smells and chemicals at this point (liver).