Carrageenan is one of those strange ingredients that “flies under the radar”. It doesn’t have a name that sounds like Methyldihydrobenzoacetate… and so it doesn’t “sound evil”… it sounds like it might be made from brown rice husks or something. But do you know what it is?
Most people don’t. And it’s very common in organic food products – being seen in dairy and dairy substitute products (including coconut milks – which are supposed to be made from just coconut!). It is found in items made by Silk, So Delicious, Starbucks, Horizon Organic, Zico, Blue Diamond, Pacific Natural Foods, Carnation and Tempt.
It turns out that carrageenan is a highly processed seaweed extract. Carrageenans are a family of linear sulphated polysaccharides that are extracted from red edible seaweeds. The seaweed is treated with potassium hydroxide, washed, dried, and milled.
There are various grades of carrageenan and problems have occurred because it has been found in degraded condition in foods.  One type of carrageenan is listed by the World Health Organization’s International Agency for Research on Cancer as a “possible human carcinogen.”  When you ingest the “undergraded version” of Carrageenan, it actually starts to degrade in the gastrointestinal tract and in the liver and turn into a carcinogen, resulting in a serious inflammatory agent that also can cause intestinal abnormalities.
Potentially serious harmful gastrointestinal effects of carrageenan have been indicated for decades – and numerous studies were reviewed in depth in 2001 by the College of Medicine at the University of Iowa, which found reports of intestinal lesions and colonic tumors in animal studies. 
In short, this is not really an ingredient which seems very safe to ingest. Various people are campaigning for its removal from organic / healthy foods