How Psoriasis Can Affect the Digestive System

Digestive problems such as ulcerative colitis and Crohn’s disease are common in people who also have psoriasis. However, psoriasis doesn’t directly cause these conditions.

The same genes that play a role in the development of psoriasis also play a role in the development of other inflammatory diseases, including Crohn’s disease.

There’s still a lot that needs to be learned about the association between these diseases, but both psoriasis and these gastrointestinal inflammatory conditions are believed to arise from cytokine-driven inflammation — specifically the interleukin 23 and Th17 pathways.

A 2015 study estimated that psoriasis is about 8 times more common in people with known Crohn’s disease than the general population. That same study noted that about 10% of people with Crohn’s disease have a close relative with psoriasis.

A more recent study in 2018 broke down the prevalence of inflammatory bowel diseases (IBD) in people with psoriasis more specifically. The prevalence of each bowel disease in people with psoriasis was:

• Crohn’s disease: 0.4%
• ulcerative colitis: 0.5%
• celiac disease: 2%

That same 2018 study reported that about 9.5% of people with Crohn’s disease had psoriasis, as did about 6.6% of people with ulcerative colitis.

It’s unclear which condition can come first. In some people, researchers suggest that psoriasis and inflammatory digestive diseases may develop independently of one another. In other people, psoriasis may be a red flag for underlying digestive inflammation.

When inflammation exists in the body, it can have many effects.

In psoriasis, inflammation makes itself known through skin plaques and lesions. Abdominal pain in IBD can also be caused by inflammation of the lining in your digestive tract.

Aside from pain in the abdomen, the following digestive symptoms have been reported at higher rates in people with psoriasis:

• feeling bloated or full
• diarrhea
• mucus in stool
• blood in stool
• unintentional weight loss

While a number of studies have shown that psoriasis and IBD share a link, how exactly psoriasis might cause IBD isn’t exactly clear. Overall, people with psoriasis are more likely to have other types of inflammatory conditions.

It’s difficult to get an exact number on how often people with psoriasis go on to develop IBD. However, there’s a stronger association between psoriasis and Crohn’s disease than with other inflammatory bowel conditions, such as ulcerative colitis.

On the other hand, irritable bowel syndrome (IBS) isn’t usually linked to inflammatory disease. Instead, IBS usually appears to result from things such as:

• intolerances to certain foods
• bacterial infections
• stress

There also seems to be an association between IBD and milder cases of psoriasis. A 2019 study reported that 87% of people with IBD had mild psoriasis, and 13% of people with IBD had moderate to severe psoriasis.

Psoriasis treatment may play a role in this difference, since more severe psoriasis is more likely to be controlled with systemic medications than a mild case. The systemic medications used in psoriasis can also help treat other inflammatory conditions such as Crohn’s disease and other forms of IBD.

There’s a catch to this treatment, though.

Biologics are being used more often to treat psoriasis — as well as for other genetically-mediated inflammatory conditions.

Yet, there’s some evidence that IBD can actually develop as an unusual side effect of these medications.

Referred to as a paradoxical issue because these medications can treat the very conditions they seem to cause, it appears that medications used to treat IBD such as infliximab, adalimumab, and etanercept may lead to development of psoriasis after treatment starts.

Additionally, while some reports have tried to link the psoriasis treatment tildrakizumab to the development of IBD, researchers have found it difficult to prove this link.

How digestive problems that occur alongside — or as a result of psoriasis — are treated depends a lot on what the condition is.

Inflammatory conditions such as psoriasis and IBD often occur in people with similar genetic characteristics. As such, inflammatory digestive disorders may benefit from some of the same treatments as psoriasis.

Treatments for psoriasis can vary based on the type and severity, but they can include things such as:

• exercise
• relaxation strategies
• diet changes
• topical creams including vitamin D analogues and steroids
• systemic steroids
• apremilast (Otezla)
• chemotherapy medications
• biologics

Making treatment more complicated is the fact that a number of other health problems are often found in people with psoriasis, such as:

• obesity
• metabolic syndrome
• nonalcoholic fatty liver disease
• celiac disease

If these conditions appear after or alongside psoriasis, you may need to be treated independently with medications or lifestyle changes, which may or may not have an impact on your psoriasis.

On its own, psoriasis is usually managed with one or more of the following:

• lifestyle changes
• strict skin care
• topical medications
• systemic medications
• light therapy

If you’re experiencing other health issues aside from psoriasis, these will require their own treatment. Consider consulting your healthcare team for options, which may change based on your full medical history, any new symptoms, or side effects you might develop after the initial psoriasis diagnosis.

Psoriasis is an inflammatory disease. Where there’s inflammation in one area of the body, there’s usually inflammation in other areas, too. Psoriasis and inflammatory bowel disorders are often linked together, although the relationship between these conditions outside of their shared genetic and inflammatory origins isn’t well understood.

Treatment may depend on the symptoms, but can include lifestyle changes, strict skin care, or topical and systemic medications.

Consult a doctor if you have psoriasis and experience digestive problems, or if you already have IBD and you develop skin lesions.