Research connects psoriasis and gut health in two main ways. People with psoriasis tend to carry a different balance of gut bacteria from people without it, with reduced variety the finding that repeats most often, and they develop inflammatory bowel disease more often too. Each of the gut bacteria studies is a snapshot of a small group, so what exists is an association, with cause unproven in either direction. Psoriasis is driven by the immune system and affects more than skin, which is why researchers interested in its whole-body side keep returning to the gut. This guide covers what has been measured in the gut in people with psoriasis, the overlap with inflammatory bowel disease, what the leaky gut research shows, what a gut microbiome test can and cannot tell you, and what trials of probiotics have found. How the gut and skin communicate more generally is covered in our guide to the gut-skin axis.
Is psoriasis linked to gut health?
The largest sequencing study so far compared 53 people with untreated plaque psoriasis against 52 people without it, matched for age, sex and weight, in Denmark. The psoriasis group had fewer types of gut bacteria and a different overall mix, and the difference held when patients were compared with partners living in the same home, a comparison that strips out much of what shared meals and shared environments could otherwise explain.
An earlier Spanish study pointed the same way. Nineteen people with psoriasis were compared against 20 without, and again the psoriasis group showed a less varied gut microbiome. A varied gut tends to be the resilient kind, because different bacterial groups do different work, and losing variety shows up across many inflammatory conditions rather than being unique to psoriasis.
Which bacteria change is where the picture blurs. A 2025 review that gathered a decade of these studies found consistent evidence that gut bacteria differ in psoriasis, and much less agreement on which groups rise or fall from one study to the next. Until larger studies agree, no specific bacterial pattern can be called the psoriasis signature, and reduced variety, the most repeated finding, has not been validated as a marker of psoriasis or of how severe it is.
Is psoriasis linked to Crohn's disease and ulcerative colitis?
Yes, and this link rests on far more data than the gut bacteria studies. An analysis pooling nine studies covering more than 7.7 million people found that people with psoriasis were around two and a half times more likely to develop Crohn's disease, and around 1.7 times more likely to develop ulcerative colitis, than people without psoriasis. Both are forms of inflammatory bowel disease (IBD), long-term conditions in which the immune system inflames the bowel.
Those figures come from health records, which show who develops which conditions over time. The gut bacteria research is a separate and much smaller body of evidence, and it echoes the overlap. In a 2015 study from New York, people with recent, untreated psoriatic arthritis, the joint condition that develops in some people with psoriasis, had less varied gut bacteria than healthy people, with several generally beneficial groups depleted. The researchers noted that the pattern looked like the one already described in IBD.
If you have psoriasis and ongoing bowel symptoms, such as diarrhoea that keeps returning, abdominal pain or blood in your stool, tell your GP about both conditions together, because the raised IBD risk is specific enough to be worth assessing properly. Persistent bowel symptoms are far more often caused by irritable bowel syndrome, which is a different condition from IBD. Our guide to the difference between IBS and IBD explains how doctors tell them apart.
Can a leaky gut cause psoriasis?
Leaky gut is the popular name for increased intestinal permeability, where the lining of the gut lets more of the gut's contents pass into the bloodstream than it should. Psoriasis is one of the few skin conditions where this has been measured in people rather than assumed. A Polish study measured claudin-3, a protein released from the seals between gut lining cells, in the blood of 60 people with psoriasis and 30 without. Levels were higher in the psoriasis group, and higher levels went along with more severe skin disease.
The same team went on to study 114 people with psoriasis and found that those whose blood markers pointed to a more permeable gut lining also reported more digestive symptoms and carried more inflammation. Both studies come from a single research group, and blood markers measure the gut lining indirectly. This is early research, and it needs repeating by other teams before it can carry much weight.
Neither study can show the order of events. Psoriasis drives inflammation through the whole body, and that inflammation could be altering the gut lining rather than the gut lining feeding the psoriasis. No study has shown that repairing the gut lining improves psoriasis, which is the claim that gut-healing programmes sold online rest on. The lining can become more permeable for many reasons, and our guide to what causes leaky gut covers them.
Can a gut microbiome test help with psoriasis?
A gut microbiome test sequences the bacterial DNA in a stool sample to show which species are present, how diverse the overall community is, and whether the groups that psoriasis studies keep finding depleted are low in yours. For psoriasis, that means you can see whether your own gut shows the kind of pattern those sequencing studies describe, reduced variety most of all, and compare your profile against research involving people with and without skin conditions.
The limits are set by the research, not the technology. A gut test cannot diagnose psoriasis, because psoriasis is diagnosed by a GP or dermatologist examining your skin. It cannot show that your gut caused your psoriasis, because no study has established cause. Nor can it promise that a different gut would mean clearer skin. What it offers is a measurement of a side of the condition you cannot otherwise see. If that is what you are weighing up, gut microbiome testing for psoriasis explains what our test measures and reports for skin.
Can improving your gut health help psoriasis?
Do probiotics help reduce psoriasis symptoms?
Trials have mostly tested supplements containing live bacteria, usually Lactobacillus and Bifidobacterium species, taken alongside normal treatment. A 2024 pooled analysis of seven randomised trials found that psoriasis severity scores fell further with the supplements than with placebo, and a blood marker of inflammation fell as well. The share of people whose skin reached a marked improvement was not clearly better than with placebo, and the trials were small, with different species, doses and lengths.
Individual trials disagree. The longest, a Brazilian trial that followed 103 people for six months, found that a Lactobacillus supplement made no difference to skin severity compared with placebo. The evidence here is mixed, and it amounts to a few hundred people across a handful of small trials.
None of this touches treatment. NICE, which sets treatment guidance for the NHS, recommends creams and ointments first for psoriasis, then light therapy and specialist medicines where more is needed, and no gut-based option appears anywhere in that guidance. No supplement is licensed to treat psoriasis in the UK, and no study has shown that changing the gut improves psoriasis in a way that could replace any part of treatment. If you take a specialist medicine such as methotrexate or a biologic injection, keep taking it exactly as prescribed, and take any questions about your gut to the specialist team or a pharmacist.
When should you seek medical advice about psoriasis?
Joint pain, stiffness or swelling, or a finger or toe that has puffed up, deserves a prompt GP appointment, because these can be early signs of psoriatic arthritis and treating it early protects the joints. If your skin suddenly turns red, painful and widespread, or sheets of small pus-filled spots appear and you feel unwell or feverish, get medical help the same day, because the rare widespread and pustular forms of psoriasis can be medical emergencies. If psoriasis is dragging your mood down or changing how you live, say so at an appointment, because NHS care treats the mental weight of skin disease as part of the condition. A GP can also step treatment up when what you are using is not working. Nothing in gut research is a reason to delay any of this, and nobody should stop a prescribed psoriasis treatment on the strength of a gut test or a gut study.
This guide is for information only and does not replace medical advice. Speak to your GP or pharmacist about your own symptoms.
Sources
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