Fasting and Skin Conditions: Why Eczema and Catarrh Were Among the First Targets

When Upton Sinclair published The Fasting Cure in 1911, he was writing from personal experience and from 277 reader-reported fasting cases. Among the conditions most frequently cited as improved by fasting were skin problems — particularly eczema — and catarrh, a persistent inflammation of the mucous membranes of the head and throat. Over a century later, modern research on inflammation and gut health offers some explanation for why these conditions appeared on that list.

Historical Context: The 1911 Cases

Sinclair collected fasting reports from readers after an article he wrote for Cosmopolitan generated 600 to 800 letters. Of the 109 people who reported outcomes, 100 said they had experienced benefit from their fast. Skin diseases — with eczema specifically named — appeared among the conditions that people reported as improved. Catarrh, a condition involving chronic mucus overproduction and inflammation of the nasal passages, throat, and sinuses, was also frequently cited.

Sinclair's explanation for these results was grounded in his theory of autointoxication: the idea that chronic overeating led to fermentation in the digestive tract, producing toxins that the body could not eliminate fast enough. In his view, this toxic overload was the underlying cause of many chronic conditions — including those that showed up on the skin and in the mucous membranes.

"The body does not begin to consume itself in a fast. It begins to consume its diseased tissue, its accumulated waste matter." — Upton Sinclair, The Fasting Cure (1911)

From Sinclair's perspective, the skin was one of the body's elimination channels. When internal organs — the liver, kidneys, and gut — were overloaded with toxins, those toxins would attempt to exit through the skin instead. Eczema, in this framework, was a visible sign of internal overload. Giving the digestive system complete rest through fasting allowed the body to redirect its resources toward clearing that backlog.

Catarrh: Chronic Inflammation of the Airways

Catarrh was an extremely common complaint in the early twentieth century. It refers to the persistent overproduction of mucus in the nasal passages, sinuses, throat, or lungs. Readers writing to Sinclair frequently described it as one of their most debilitating long-standing problems — conditions they had lived with for years and that doctors had been unable to resolve.

Sinclair's theory here was similar to his skin explanation. Chronic overfeeding kept the digestive and immune systems in a permanent state of mild inflammation. Fasting removed the inflammatory stimulus, giving the mucous membranes time to settle. Readers who fasted for five to twelve days frequently reported that catarrh that had been present for years cleared or dramatically reduced within days of beginning a fast.

Whether Sinclair's autointoxication theory maps precisely to modern biochemistry is debatable. But the underlying observation — that gut inflammation and skin or airway inflammation tend to co-occur, and that dietary changes can affect both — turns out to have substantial support in modern research.

What Modern Science Adds

The Gut-Skin Axis

Research published over the past two decades has established a clear connection between gut health and skin condition. Disruption of the gut microbiome — the community of bacteria living in the digestive tract — is associated with conditions including eczema, psoriasis, acne, and rosacea. This relationship, sometimes called the gut-skin axis, operates through inflammatory signalling: a disturbed gut produces pro-inflammatory compounds that travel through the bloodstream and can trigger skin reactions.

Fasting alters the gut environment significantly. Even short fasting periods reduce the amount of fermentable substrate in the gut, shift the composition of the microbiome, and lower systemic inflammation markers including C-reactive protein and tumour necrosis factor-alpha. These are exactly the kinds of changes that would be expected to benefit inflammatory skin conditions.

Autophagy and Skin Renewal

Fasting triggers autophagy — the cellular recycling process in which the body breaks down and removes damaged or dysfunctional cell components. This process is particularly relevant to skin because skin cells renew continuously. Efficient autophagy helps clear damaged proteins that accumulate with age and inflammation, and supports the maintenance of healthy skin barrier function.

Reducing Dietary Triggers

One mechanism that Sinclair did not have the language for — but which modern nutritional research supports — is simply the removal of inflammatory dietary inputs. Many eczema sufferers find that common dietary triggers, including sugar, refined carbohydrates, and certain food additives, worsen their symptoms. A fasting period removes all food inputs entirely, which can produce a noticeable reduction in symptoms. When the fast is broken and food is reintroduced one category at a time, it can also help identify which foods are contributing to flares.

Sinclair's Most Notable Observations

Several specific observations from the 1911 cases remain interesting in light of current understanding:

The speed of response: Many readers reported that skin and catarrh symptoms began improving within the first week of fasting — often faster than improvements in joint pain or digestive conditions. This fits with modern understanding that systemic inflammation markers can begin falling within a few days of fasting.

The need to maintain food quality after the fast: Sinclair repeatedly emphasised that results were only maintained if people changed their diet after the fast. Those who returned to the same eating patterns found their symptoms returned. This aligns with modern research showing that dietary quality post-fast determines whether benefits are sustained.

The link between digestive symptoms and skin symptoms: Many of Sinclair's correspondents described having both digestive problems and skin conditions. They noted that both improved together during the fast. Modern gastroenterology recognises this co-occurrence clearly — eczema is significantly more common in people with irritable bowel syndrome and inflammatory bowel disease than in the general population.

What to Know If You're Fasting With a Skin Condition

A few considerations worth keeping in mind:

• Some people experience a temporary worsening of skin symptoms in the first days of a fast. This was noted by Sinclair as well and is sometimes attributed to the initial mobilisation of stored inflammatory compounds. It typically resolves as the fast continues.
• The post-fast diet matters more than the fast itself. Fasting creates a reset, but returning to inflammatory foods — seed oils, sugar, refined grains — quickly reverses the benefits.
• Very long fasts are a different category. Most of what Sinclair documented and most of what is practised today involves fasts of one to five days. Extended fasting beyond this should not be undertaken without medical guidance.
• Skin conditions with an autoimmune component (such as psoriasis) have different mechanisms than eczema, and the evidence for fasting specifically is less developed, though the general inflammatory framework applies.

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Frequently Asked Questions

Did Upton Sinclair say fasting cures eczema?

Sinclair did not claim fasting cured anything in a clinical sense. He reported what readers described in letters and what he observed personally. Eczema appeared among the conditions most commonly mentioned as improved. He framed this in terms of his autointoxication theory rather than as a guaranteed medical outcome.

How long did people in Sinclair's cases fast for skin conditions?

The average fast length in the 277 cases was approximately six days. Most skin improvements were reported within the first week, though Sinclair noted that maintaining a clean diet after the fast was essential for lasting results.

What is catarrh and does fasting really help it?

Catarrh is persistent overproduction of mucus in the nasal passages, throat, or airways. It often has a dietary component — particularly dairy, sugar, and refined carbohydrates are associated with worsening mucus production. Fasting removes these inputs entirely, which may explain the rapid improvements many of Sinclair's correspondents reported.

Is there modern research on fasting and eczema specifically?

Formal clinical trials on fasting and eczema are limited. Most of the modern evidence comes from research on gut health, systemic inflammation, and dietary elimination protocols. The biological mechanisms supporting Sinclair's observations — gut-skin axis, autophagy, reduced systemic inflammation — are well-established, even if fasting-specific eczema trials are sparse.

Should someone with eczema try fasting?

That is a question for a healthcare professional who knows the individual's full picture. What the historical cases and modern mechanisms suggest is that the connection between diet, gut health, and skin inflammation is real and worth exploring. Anyone on medication for a skin condition should consult their doctor before changing their diet significantly.

Related Articles

• How fasting clears toxins from your body
• Autointoxication: the Victorian theory that explains why fasting works
• Does intermittent fasting reduce inflammation?

This article draws on historical research from 1911 and is for informational purposes only — not medical advice. Always consult a qualified healthcare professional before making any dietary changes.

Sinclair, U. (1911). The Fasting Cure. Mitchell Kennerley.