This is BAD! Our iguana, Iggi, threw up a few years ago. Your iguana could either have a hair caught in it's throat (if your ig has the opportuntity to eat some human hair), or it could have twisted gut. Our iguana had a loop of intestine twisted, and the food we were giving her caused gas. It was the small diced potatoes and corn in a can of mixed vegetables. The gas had no where to go, and so our ig threw up. We took her immediately to our herp vet, who prescibed Mylacon drops for gas relief for children. We gave her a few drops, twice a day, and it worked. We also stopped feeding her gassy foods. I recommend a herp vet visit ASAP. Good Luck. Let us know how it turns out.
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Lamar, Debbie, Nathaniel and Iggi :>~