Carrageenan comes from a red seaweed (genus Chondrus and others, including Irish moss). Manufacturers use it because it thickens, gels, and stabilizes — perfect for making almond milk feel creamy without dairy, or deli meat hold its shape.
The controversy hinges on two different forms: food-grade carrageenan (the kind used in food) is high-molecular-weight and not absorbed by your gut. Poligeenan, also called 'degraded carrageenan', is low-molecular-weight, inflammatory in animal studies — and not approved for food anywhere. They're chemically related but regulated as separate substances [1].
The European Food Safety Authority (EFSA) re-evaluated food-grade carrageenan (E 407) in 2018 and reaffirmed its safety at current use levels, while flagging gaps in toxicological data, especially for infants [1]. The FDA includes carrageenan on its food additive list and treats it as Generally Recognized as Safe within established limits [2].
Some small studies have suggested food-grade carrageenan may aggravate symptoms in people with IBD, but the evidence is limited and mixed. If you have a sensitive digestive system, you may notice it. Most people won't.