Is Carrageenan Safe? 
You may see references in magazines and on the Internet that caution consumers against the consumption of carrageenan due to concerns about the potential for gastrointestinal effects (including malignancies). These cautions were based on the conclusions of a literature review by Dr. Joanne Tobacman and published in Environmental Health Perspectives in October 2001. Recent published information has become available that should allay your concerns about the consumption of carrageenan.

Overall, the JECFA concluded that there was no concern to the continued consumption of carrageenan and assigned it to the group "Acceptable Daily Intake - not specified". This classification is used when the JECFA has determined that a food additive does not represent a hazard to health. It also allows for the use of the additive at the level necessary to achieve the technical or functional effect in food, also referred to as the level of Good Manufacturing Practices (GMP). The complete report of this review was made publicly available in 2003 and therefore post dates the review by Dr. Tobacman.

For more information on human consumption and carrageenan, see the JECFA Summary or review the adjacent reports. 

JECFA Summary