Introduction
Social media occasionally promotes unusual “natural skincare” practices, including claims that baby feces or even one’s own feces may benefit the skin because they are “organic” or contain “natural microbiome bacteria.”
Scientifically and physiologically, however, feces is a biological waste product designed to be eliminated from the body, not applied onto the skin.
Although infant stool differs somewhat from adult stool in microbiome composition, both still contain microbes, digestive residues, nitrogenous metabolites, enzymes, inflammatory compounds, and waste byproducts capable of damaging the skin barrier.
Public discussions and media reports regarding so-called “feces facials” have also highlighted growing concern surrounding this unsafe skincare trend.
The Misconception About “Organic” Biological Waste
Some individuals promote the idea that applying one’s own feces is safer because it is “natural,” “organic,” or produced by the same body.
Physiologically, this reasoning is incorrect.
A substance being natural or produced by the body does not automatically make it safe for skin exposure.
For example:
sweat may irritate skin,
excess sebum may contribute to acne,
urine and feces are waste elimination products,
and vomitus contains stomach acid capable of tissue irritation.
Feces remains biological waste regardless of whether it originates from an infant or the same individual applying it.
The body is specifically designed to:
remove feces from the intestine,
prevent prolonged skin exposure,
and maintain separation between gut microbes and external tissues.
If feces were beneficial for skin, conditions such as diaper dermatitis would not be common clinical problems.
What Is Feces Physiologically?
Feces is composed of:
water,
undigested food residues,
dietary fiber,
dead intestinal epithelial cells,
gut bacteria and microbial byproducts,
bile pigments,
small amounts of digestive enzymes,
and nitrogen-containing metabolites.
The intestine is specially adapted to tolerate these substances through mucus barriers, immune regulation, and microbiome balance. Facial skin does not possess the same protective environment.
Nitrogenous Waste and Ammonia Formation
Proteins contain nitrogen within amino acids. During metabolism:
proteins are broken down into amino acids,
nitrogen is removed through deamination,
and toxic ammonia is initially produced.
Most ammonia is later converted by the liver into urea for safer excretion.
However, inside the intestine, gut bacteria continuously metabolize proteins and nitrogen-containing compounds, producing small amounts of ammonia and related metabolites locally. Some of these compounds remain within stool.
Ammonia contributes to skin irritation by:
increasing skin pH,
weakening the epidermal barrier,
activating inflammatory pathways,
and increasing enzyme-related tissue damage.
This mechanism contributes significantly to conditions such as diaper dermatitis in infants.
Why Digestive Enzymes Damage Skin
Feces may contain residual digestive enzymes such as:
proteases, which break down proteins,
and lipases, which break down fats.
These enzymes are beneficial inside the digestive tract but potentially harmful during prolonged skin exposure.
When applied onto facial skin, they may:
damage structural skin proteins,
disrupt protective lipids,
increase transepidermal water loss,
and trigger irritation and inflammation.
Scientifically, stool often irritates skin more than urine because stool contains enzymes, microbes, bacterial metabolites, and ammonia-related compounds simultaneously.
Microbes Present in Feces
Neither infant stool nor adult stool is sterile.
They may contain organisms such as:
Escherichia coli,
Enterococcus species,
Bifidobacterium species,
Lactobacillus species,
Candida species,
and viral particles during gastrointestinal infections.
Although some intestinal microbes may be beneficial within the gut, this does not mean they are safe when transferred onto facial skin.
Potential complications may include:
irritant dermatitis,
folliculitis,
secondary bacterial infection,
fungal overgrowth,
acneiform eruptions,
periorificial dermatitis,
and eye contamination with conjunctivitis risk
Why Feces Produces Odor
Fecal odor mainly results from bacterial metabolism of proteins and organic matter, producing volatile compounds such as:
hydrogen sulfide,
ammonia,
indole,
skatole,
and volatile fatty acids.
These compounds are byproducts of microbial metabolism and biological waste processing.
The Misunderstanding About “Microbiome Skincare”
Modern dermatology does study:
probiotics,
postbiotics,
and skin microbiome regulation.
However, laboratory-formulated microbiome therapies are highly purified and scientifically controlled.
Applying raw fecal material is entirely different because it contains uncontrolled organisms, enzymes, toxins, and waste metabolites.
The concept of a “feces facial” incorrectly confuses microbiome science with direct exposure to biological waste.
Conclusion
From a physiological and dermatological perspective, applying baby feces or human feces onto the face is unsafe and unsupported by medical evidence.
Stool remains a biological waste product containing microbes, digestive enzymes, nitrogenous metabolites, and inflammatory compounds capable of disrupting the skin barrier and increasing infection risk.
The presence of beneficial gut bacteria inside the intestine does not translate into skincare benefits when feces is externally applied to the skin.
References
Atherton DJ. A review of the pathophysiology, prevention and treatment of irritant diaper dermatitis. Current Medical Research and Opinion. 2004
Blume-Peytavi U, et al. Skin care practices for newborns and infants: review of the clinical evidence for best practices. Pediatric Dermatology. 2016
Hall JE. Guyton and Hall Textbook of Medical Physiology. 14th ed. Elsevier. 2021
Nelson Textbook of Pediatrics. Elsevier. 2023
The Guardian. “A poo facial mask – smaller pores, yes, but do you really want faeces on your face?” 2019