Lysozyme

If you have persistent loose stools or cramping, checking for bowel inflammation can help narrow down the cause. Stool lysozyme has been studied for this purpose, but results overlap between different conditions and healthy people. Its value for diagnosing disease or guiding treatment remains uncertain.

This is an exploratory marker. Commercial testing is available, but there are no universally accepted clinical decision thresholds or proven targets for improving health. Calprotectin has much stronger evidence for assessing bowel inflammation, and there is no established preventive benefit from measuring lysozyme while you feel well.

Where It Comes From

Lysozyme breaks down part of the bacterial cell wall, helping kill susceptible bacteria. Your digestive tract gets it from immune cells, including neutrophils and macrophages, and from cells in the gut lining. Paneth cells release lysozyme and other defensive proteins from small pockets in the small intestine's lining.

Healthy people can have measurable lysozyme in their stool. A study using a different antibody-based laboratory method found amounts consistent with substantial local production in the digestive tract. That doesn't establish that most stool lysozyme comes from the lining rather than immune cells, and a stool result cannot identify which cells released it.

What This Test Measures

This test measures lysozyme protein in stool using ELISA and reports the concentration in ng/mL. ELISA uses antibodies to detect the protein. It does not directly measure how effectively the enzyme breaks down bacteria. Many older studies measured enzyme activity, so their findings provide background evidence but their numerical results are not interchangeable with this test.

Crohn's Disease and Ulcerative Colitis

Crohn's disease and ulcerative colitis are the main forms of inflammatory bowel disease. Stool lysozyme has been investigated in both, with inconsistent results.

One study examined 76 stool samples from 31 people with ulcerative colitis. Lysozyme had a weak relationship with a disease activity score that combined symptoms and laboratory findings. Values were higher during active disease, but the difference from remission was not statistically reliable. Calprotectin, lactoferrin, and neutrophil elastase separated the two states more clearly.

That study doesn't establish a useful lysozyme target for your result or show that adding it to calprotectin improves treatment decisions. Current bowel disease monitoring guidance relies on symptoms, better-validated biomarkers, and endoscopy or imaging when needed.

Diarrhea and Gut Transit

An older study found increased stool lysozyme activity in inflammatory bowel disease, but similar increases occurred in people with diarrhea from other causes. It measured enzyme activity rather than the protein concentration reported by this ELISA. The finding supports caution about specificity; it doesn't establish that every bout of diarrhea raises this test's number.

Water content also matters. Instructions for a commercial stool lysozyme ELISA warn that severe diarrhea can produce a low result despite intestinal inflammation. A loose sample therefore cannot be interpreted with a simple rule that diarrhea always pushes lysozyme up.

Colon Cancer Screening

Stool lysozyme has not proved useful for colorectal cancer screening. An older study comparing 23 people with colorectal cancer and 39 healthy people found no meaningful difference between the groups. Its measurement and reporting approach did not validate this particular ELISA. A lysozyme result cannot reliably identify or exclude colorectal cancer.

Gut Barrier Research

A 2026 study of 50 healthy adults included stool lysozyme among several markers examined alongside plastic particles in stool and urine. It did not establish that a lysozyme result measures plastic exposure or how easily substances cross the intestinal lining. Stool lysozyme remains unvalidated as a stand-alone test of intestinal permeability.

Human biopsy studies have also examined lysozyme in microscopic colitis. This condition requires examination of bowel tissue under a microscope. The studies found different patterns of lysozyme in lining cells and immune cells across its two main forms. Those tissue findings cannot be transferred directly to a stool result.

When Results Can Be Misleading

• Stool consistency and current symptoms: diarrhea changes the context for interpretation, and very watery stool can yield a low result despite inflammation.
• Sample preparation and storage: the amount sampled, mixing, extraction, dilution, and storage conditions affect the reported concentration.
• ELISA interference: substances in a stool sample can interfere with antibody-based measurement and produce falsely high or low results.
• Measurement limits: a result below the assay's quantifiable range does not prove that no lysozyme is present. A sample above its measuring range may require laboratory dilution and repeat analysis.
• Differences between laboratories: extraction procedures, antibodies, and calibration can differ even between ELISA tests. Matching units alone does not make results interchangeable.

What Changes Over Time Can Mean

Repeated results may document a change in stool lysozyme, but research has not established how much change reliably represents worsening disease or healing. A fall can occur without a demonstrated improvement in symptoms. A low result also does not diagnose weak gut defenses. Trends need to be interpreted alongside symptoms and established measures of inflammation.