Carrageenan, gut inflammation and allergic reactions reviewed
What it found
In lab tests and animals, carrageenan triggered inflammation and changed gut bacteria.
In people, a small trial found carrageenan capsules were linked to earlier relapse of ulcerative colitis, and two case reports described allergic reactions.
What they found
Studies in people
Ulcerative colitis trial
In a randomised, double-blind trial, 12 people with ulcerative colitis in remission followed a no-carrageenan diet and took either placebo or carrageenan capsules for up to a year. No one in the placebo group relapsed, while three in the carrageenan group relapsed, and only that group showed increased levels of inflammation markers like IL6 and faecal calprotectin.
Allergic reactions
Two case reports described allergic reactions after taking in carrageenan: a 26-year-old woman had anaphylaxis during a barium enema and later reacted to processed milk products, and a 10-month-old infant developed lip swelling after eating cake icing. Both tested positive on skin prick tests for carrageenan.
Animal and lab studies
Inflammation in lab tests
In lab tests on human colon cells, carrageenan switched on inflammatory pathways and increased production of the inflammatory signal IL8. It also affected the tight junctions between cells, which may make the gut barrier leakier.
Gut bacteria changes
In a lab model using human fecal samples, kappa and lambda carrageenans increased Bacteroides, while iota carrageenan reduced Faecalibacterium, which is known for anti-inflammatory properties. Animal studies also found carrageenan altered gut bacteria and promoted intestinal inflammation.
Colitis in animals
In rats given degraded iota-carrageenan in drinking water for 55 days, all rats except controls developed diarrhea, and colon length decreased, especially in the group that received the 40 kDa form. The severity of inflammation was strongly linked to the molecular size of the degraded carrageenan.
Other findings
Alpha-gal syndrome link
Carrageenan contains the alpha-gal epitope, which is linked to delayed allergic reactions to red meat after tick bites. The authors suggest carrageenan may be a potential source of exposure to this epitope.
What the authors conclude
“Until no data on the safety and the effects of carrageenan are available, a reduction of human exposure to CGN limiting ultra-processed foods is advisable.”
Also in their conclusions
- They say that lab and animal studies suggest carrageenan has a pro-inflammatory effect, but these results cannot be directly applied to humans.
- They advise limiting human exposure to carrageenan by reducing the consumption of ultra-processed foods until more safety data are available.
- They call for future research using models that mimic human digestion and for studies on how much carrageenan people actually eat.
How it was done
Carrageenan use in processed foods has risen with the Western diet, and there is debate about its safety. The authors wanted to review the evidence on its role in inflammatory bowel diseases and allergic reactions.
They reviewed published studies on carrageenan, including lab tests on cells, experiments in animals, a small randomised trial in people with ulcerative colitis, and case reports of allergic reactions.
What it can’t tell you
- The small trial in people with ulcerative colitis had only 12 participants, so it cannot show how carrageenan affects the general population.
- The case reports of allergic reactions cannot prove that carrageenan causes allergy in most people.
- Lab and animal results cannot show what happens in people because human digestion and gut bacteria are different.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- University of Milan, Italy
The paper
- Title
- The Role of Carrageenan in Inflammatory Bowel Diseases and Allergic Reactions: Where Do We Stand?
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Borsani B, De Santis R, Perico V, et al (2021). The Role of Carrageenan in Inflammatory Bowel Diseases and Allergic Reactions: Where Do We Stand?. Nutrients. doi:10.3390/nu13103402Free full textPubMed 34684400DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error