An increased number of reports have appeared in the literature describing the harmful effects of degraded and undegraded carrageenan supplied to several animal species in their diet or drinking fluid. The harmful effects include foetal toxicity, teratogenicity, birth defects, pulmonary lesions, hepatomegaly, prolonged storage in Kupffer cells, ulcerative disease of the large bowel with hyperplastic, metaplastic, and polypoidal mucosal changes, enhancement of neoplasia by carcinogens, and, more ominously, colorectal carcinoma. Degraded carrageenan as a drug or food additive has been restricted in the United States by the FDA, but undegraded carrageenan is still widely used throughout the world as a food additive. Its harmful effects in animals are almost certainly associated with its degradation during passage through the gastrointestinal tract. There is a need for extreme caution in the use of carrageenan or carrageenan-like products as food additives in our diet, and particularly in slimming recipes.