Psoriasis is a common, chronic inflammatory skin condition characterized by patches of red, thickened skin covered with silvery scales. Probiotics are live microorganisms, often bacteria or yeasts, which, when administered in adequate amounts, confer a health benefit on the host, primarily by influencing the gut microbiome. The interest in probiotics as a supplementary treatment for psoriasis stems from the understanding that inflammation is a systemic issue, suggesting a link between gut health and skin disease activity. This connection has led researchers to explore whether modulating the microbial environment can offer a new approach to managing this condition.
Understanding Psoriasis and the Immune System Link
The visible skin symptoms of psoriasis are driven by a complex, dysregulated immune response that occurs throughout the body. At its core, the condition is mediated by T-cells, a type of white blood cell responsible for immune surveillance. Specifically, a subset known as T-helper 17 (Th17) cells plays a central role in the disease’s pathology.
These Th17 cells produce large amounts of inflammatory signaling molecules, or cytokines. Key cytokines involved include Interleukin-23 (IL-23) and Tumor Necrosis Factor-alpha (TNF-alpha), which promote the survival and activation of the Th17 cells. Another cytokine, IL-17A, directly signals skin cells, called keratinocytes, causing them to multiply rapidly and leading to the characteristic thick, scaly plaques. This cycle of T-cell activation and cytokine release perpetuates chronic inflammation, which is a systemic issue.
The Gut-Skin Axis: The Mechanism of Influence
A physiological connection exists between the intestinal microbiome and skin health, a concept known as the gut-skin axis. In psoriasis, an imbalance in the gut microbial community, termed dysbiosis, is often observed. This altered microbial composition can compromise the integrity of the intestinal lining.
When the gut barrier is weakened, bacterial products, such as Lipopolysaccharide (LPS), can pass through the intestinal wall and enter the bloodstream. This LPS acts as a potent systemic inflammatory signal, traveling throughout the body and contributing to chronic, low-grade inflammation. These signals can then exacerbate the T-cell activation and cytokine cascade driving psoriatic skin lesions.
Conversely, beneficial gut microbes produce metabolites like Short-Chain Fatty Acids (SCFAs) through the fermentation of dietary fiber. SCFAs are known to have anti-inflammatory properties and can act on immune cells far from the gut. By promoting a balanced gut environment, these metabolites can help regulate distant immune responses, potentially dampening the systemic inflammation associated with psoriasis.
Scientific Evidence and Clinical Findings
Clinical research has begun to explore the direct effects of probiotic supplementation on psoriasis severity. Several randomized controlled trials have demonstrated that administering probiotics as an add-on to standard therapy can lead to measurable improvements in patients. These improvements are often assessed using the Psoriasis Area and Severity Index (PASI) score, a standard measure of disease extent and severity.
For example, one study using a multi-strain probiotic containing species like Bifidobacterium longum, Bifidobacterium lactis, and Lactobacillus rhamnosus reported a significant reduction in PASI scores in the treatment group. Other trials have found that probiotic use lowered levels of inflammatory markers in the blood, including high-sensitivity C-reactive protein (hs-CRP) and IL-1β, as well as the bacterial product LPS. These findings suggest that probiotics may be working by reducing systemic inflammation originating from the gut.
While specific strains like Lactobacillus acidophilus and Bifidobacterium bifidum have been included in successful multi-strain blends, the optimal probiotic strain, dosage, and duration of treatment remain undetermined. The current evidence is limited by a small number of studies, small sample sizes, and clinical variation in the types of probiotics used. More standardized, large-scale studies are necessary to confirm their role as a therapeutic agent for improving clinical outcomes and inflammatory status.
Practical Considerations for Probiotic Use
Patients considering adding a probiotic to their regimen should view it as a complementary strategy, not a replacement for prescribed psoriasis treatments. While probiotics are generally considered safe, some individuals may experience mild gastrointestinal side effects, such as temporary bloating or gas, as their body adjusts to the new microbial input.
It is important to select a high-quality product, which often means paying attention to the Colony Forming Units (CFU) listed on the label. Many experts recommend a product that guarantees a minimum number of live organisms, typically in the billions, until the expiration date. Some probiotic strains require refrigeration to maintain their viability, so consumers should check the packaging for specific storage instructions. Consulting with a dermatologist or gastroenterologist before beginning any new supplement is advisable to ensure it is appropriate and will not interfere with existing medications.