On the other hand, poligeenan, or "degraded" carrageenan, consists of smaller fragments, and for decades this form has been used to intentionally induce inflammation in animal subjects for research purposes. It's also carcinogenic. Poligeenan is not permitted in food.
Veterinary nutritionists, pet food manufacturers, and, of course, producers of carrageenan assert that food-grade carrageenan is completely safe for pets to eat. However, even food-grade carrageenan is not perfectly pure; it contains a "low percentage" of the smaller, more damaging fragments. This may explain why even food-grade carrageenan can cause problems.