The biology of the human body is complicated and sometimes this complexity creates unexpected connections. Case in point, the link between gut and skin health. In 1930, dermatologists John H. Stokes and Donald M. Pillsbury published a paper outlining their theory of how the gut, brain, and skin are connected.

They linked emotional states of anxiety, depression, and worry to changes in the gastrointestinal track function and the microbes that live there. This connection, they believed, increases local and systemic inflammation. They wrote that the gut provides an important link between emotional states and skin problems.

Though the mainstream dermatological practice has largely ignored or forgotten this brain-gut-skin theory, much of the original theory has been confirmed by later research.

It is evident that gut microbes and oral probiotics could be linked to the skin, and particularly acne severity, by their ability to influence systemic inflammation, oxidative stress, glycemic control, tissue lipid content, and even mood.

Bowe, W., Patel, N. & Logan, A. Acne vulgaris, probiotics and the gut-brain-skin axis: from anecdote to translational medicine. Beneficial Microbes 5, 185199 (2014). https://www.ncbi.nlm.nih.gov/pubmed/23886975

While Pillsbury, Stokes, and other scientists provided compelling data to support the link between skin problems and gut issues, mainstream dermatologists largely ignored this because of quackery.

In the early 20th century, quacks and charlatans were promoting their thoroughly-debunked ‘autointoxication’ theories. They claimed that the gut is full of undigested and rotten food and the poisons leak through the gut and poison the body. They hawked colon cleanses and various detoxes to cure this common ill.

Unfortunately, the legitimate link between gut and skin issues got tarnished by quacks and baby was washed out with the bathwater. Now, 70 years later, this idea finally starts getting the attention it deserves.

Evidence linking gut issues to skin problems

Let’s start with a brief look at the studies connecting gut issues to skin problems. This evidence was helpfully combined in Dr. Bowe’s 2014 paper “Acne vulgaris, probiotics and the gut-brain-skin axis: from anecdote to translational medicine.”

• A Chinese study of over 13,000 adolescents found that digestive problems were more common among people with sebaceous gland disease (seborrhea, seborrheic dermatitis, acne, androgenetic alopecia, and rosacea). In particular, abdominal bloating was 37% more common among people suffering from these skin problems.
• One of the few studies on acne patients comes from South Korea. In this 2010 study the researchers gave people with mild to moderate acne a fermented milk beverage with or without lactoferrin, an anti-inflammatory component of milk. The results showed 33% reduction in pimple count as a consequence of the fermented dairy drink. Adding lactoferrin improved results further with 56% reduction in pimple count. Lactoferrin has a potent anti-inflammatory effect, so combining it with probiotic drink hits acne from two sides. Interestingly, sebum production dropped significantly in both groups, and sebum composition shifted positively (reduction in free fatty acids, an increase of which has been implicated in acne).
• Another relevant study comes from Russia. This study of 113 acne patients showed that 54% had some form of disturbance in the gut microflora. The authors noted that adding ‘intestinal microflora-correcting agents’ to standard treatment halved the treatment time. It’s not clear what they mean by intestinal microflora-correcting agents; I presume either probiotics or antibiotics.
• One of the most convincing studies comes from Italy. The researchers looked at the prevalence of SIBO among acne rosacea patients and what effect eradicating SIBO with antibiotics has. The study found that SIBO was nearly 10 times more prevalent among patients than controls (46% vs. 5%). Antibiotics eradicated SIBO in 17 of 20 cases. This led to complete clearing of rosacea in 71% of the patients and significant improvements in 22%. In other words, the treatment helped 93% of the rosacea patients with SIBO. There was no change in the placebo group. The evaluation was done 1 month after the antibiotic treatment, so the results lasted at least for some time. How do we know these results are due to eradication of SIBO? They also treated rosacea patients who tested negative for SIBO, and no change was seen in this SIBO negative rosacea group.
• In a study from 1916, 65% of the 57 acne patients studied showed a positive reaction to bacteria originating from the gut, but none of the control patients without skin disease reacted to the bacteria. This indicates that the bacteria may have leaked (or translocated) from the gut to the bloodstream and thus sensitized the immune system to them.
• Another older study showed that blood from 65% of the acne patients reacted to a bacterial toxin produced by E. coli (pathogenic bacteria found in the gut). Whereas none of the healthy controls showed such reactivity. This again indicates that gut content leaks to the bloodstream.
• Another old study showed that 40% of acne patients have low stomach acidity (a common risk factor in SIBO).
• Older studies also show constipation is more common among people with acne; Stokes and Pillsbury saying it’s the rule rather than an exception in acne.
• Finally, there’s a report from a physician in the sixties who administered probiotic supplement to 300 acne patients. He reported that 80% showed some form of improvement on their skin.

Scientifically speaking, this evidence is not rock-solid. Meaning that a scientist could easily say that the above isn’t enough to conclude that gut problems cause skin issues. And I would agree with that. However, my point is not to say there’s 100% scientifically valid evidence that gut problems cause skin problems. My point is that there’s enough evidence to suspect gut problems as an unrecognized underlying cause for acne and other skin problems.

From experience, I can say that my acne is linked to gut issues. Many people have emailed me saying they also noticed the connection, after someone pointed out the possibility to them.

I’m not saying everyone with acne also has gut problems. I’m saying this is one of the possible causes, and you should seriously look into it.

I also believe that gut issues are one explanation why people living in traditional cultures have little to no acne. As we’ll see later in this chapter, processed and Western-style food, along with antibiotic usage, is one of the main causes. Similarly, unprocessed foods contain fiber and other substances that feed the good bacteria in the gut and maintain healthy bacterial balance.