Tracing the skin as it rounds the lips and becomes the lining of the mouth and digestive tract, it seems reasonable that skin problems could continue on the inside as well. In fact, similar to the function of the skin, the lining of the intestines is tasked with keeping some things out (such as certain types of bacteria and larger molecules that may cause allergies) and allowing other things in (such as nutrients). An impairment of this function leads to increased permeability, sometimes called “leaky gut."
Certain triggers and stresses are thought to cause changes in the intestinal bacteria and disrupt the gut barrier, and this has been tied to many different diseases including inflammatory bowel disease, celiac disease, food intolerance, and small intestinal bacterial overgrowth. Interestingly, there are also non-gastrointestinal diseases on this list, including fibromyalgia, chronic fatigue syndrome, and, the focus of the current article, atopic dermatitis.
Abnormal Barrier in Atopic Dermatitis and Leaky Gut
In atopic dermatitis, the skin barrier is known to be abnormal: water escapes too easily leading to dry, itchy skin, and allergens, irritants, and bacteria can all enter, leading to an immune response and subsequent inflammation. Although there is some evidence to show that excluding foods from the diet in those without known allergy is not helpful for most, the implication of the gut in atopic dermatitis has been very difficult to shake, and many feel that diet is the “root cause.”
A study from the United Kingdom identified significantly increased intestinal permeability (leaky gut) in children with atopic dermatitis when compared to children without eczema, while another found a relationship between how leaky the gut was with how severe the eczema was--a very compelling finding, to be sure!
If leaky gut is indeed connected with atopic dermatitis, can it be treated? The answer seems to be “yes,” but with qualifications. Food allergies have been shown to cause inflammation in the gut, altering the intestinal barrier. One small study evaluated 15 children with atopic dermatitis and subjected them to a two-week elimination diet where they were only allowed to consume a highly restricted group of foods. Interestingly, 9 of the 15 patients had a significant improvement in their eczema and those who did better had improved gut barrier compared to those who didn't.
While many questions remain unanswered about diet and eczema, there is hope that a better understanding will help sort what types of dietary changes could be helpful and in what settings. Greater knowledge of the gut-skin connection has led to the introduction of probiotics. This concept relies on bacterial diversity in the gut and how this tends to be a sign of a healthy gut.
Changes in gut microbacterial diversity may affect the aspects of the immune system directly or indirectly. While the evidence on probiotics and atopic dermatitis remains somewhat confusing, the consensus currently states that probiotics are not effective for most for the treatment of established eczema but may be helpful in prevention. However, there is the suggestion that there may be different subtypes of the disease which respond better than others.
Study with Probiotics
One study administered two different strains of lactobacilli probiotic to 41 children with moderate or severe atopic dermatitis for six weeks. 14 of the 41 were tested for intestinal permeability, and about a 50% improvement was measured following treatment with probiotics, suggesting a significant improvement in gut barrier. Another study of 39 infants with eczema were randomized to receive lactobacillus rhamnosus GG for three months, and the major groups of gut and skin bacteria were analyzed. At one month, there was improved gut barrier function in the treatment group compared to those who were not treated.
It is important to remember that many unknowns remain here: the appropriate type of probiotic, the optimal dose, and duration of probiotics still require a great deal of study, but there is certainly promise in probiotic therapy.
Newer Treatments and Future of Leaky Gut
Newer treatments may also be of benefit. Gelatin tannate is able to form bonds with mucin in the mucus layers of the gut and improve the gut barrier. This may prove to be a viable option for improving gut barrier function, perhaps akin to a topical moisturizer for the skin.
Atopic dermatitis remains a complex, multi-faceted disease. Despite growing scientific interest, there are still many unanswered questions. Leaky gut represents a thought-provoking idea that has diagnostic and therapeutic implications but also raises many questions. More studies are required to determine if leaky gut is universal in AD or if there are specific subtypes for which it is relevant, and what approaches will yield the most improvement.