My iggy is nose rubbing. WHY?

My baby iggy is nose rubbing. A LOT. He's probably a few months, maybe 4, 5 or 6. He's a hearty eater. I feed him everyday--greens (usually green leaf/kale/mustard), usually yellow squash or zuchini and occasionally a fruit. He gets sprinkled calcium supplement and a sprinkled multi vitamin supplement with every meal. I have a heat light and a uvb light and defined basking/ shade areas. He has a nice big water bowl and seems to be a happy, healthy baby...but he nose rubs all the time. Usually on his drift wood branch and I find that too be so abrasive for his face. He usually rubs all the way near his eyes. I've heard that iguanas will bug out their eyes to "itch" themselves and I often see him do that before or after nose rubbing. He is also a big sneezer. I hear him sneeze more often than I've ever noticed an iguana sneeze...and he usually has crusty white salts near his nostrils. I don't think he gets too much sodium in his food though, so I'm not sure why. His cage is about 12"H x 30"L. I do intend to get a bigger cage soon. Could shedding his face make him itch possibly? Maybe that's why he nose rubs? I'd love some input!