Endolysin XZ.700 for Eczema: What a 39-Person Study Actually Found

Dr. Arsy Editorial Team · November 9, 2026

A laboratory idea can be promising without producing a clinical benefit. A 2026 trial of XZ.700, an experimental enzyme designed to target Staphylococcus aureus, enrolled 39 adults with mild-to-moderate eczema; 35 completed the study. Under the tested conditions, researchers did not demonstrate a reduction in the target bacteria or an advantage in eczema scores over the comparison cream. ^[1]

What researchers tested

XZ.700 is a recombinant endolysin: a protein engineered to damage a specific bacterial target. The idea comes from the observation that S. aureus is often found on eczema-affected skin and can contribute to inflammation. Finding a bacterium on skin, however, is not automatically the same as diagnosing an infection, and reducing a laboratory measure does not by itself establish that people feel better. ^{[1][11][12][13]}

The investigators used a randomized, blinded comparison with a vehicle—the cream base without the investigational active. In one part, different strengths were used for seven days; a later comparison evaluated the 100-microgram-per-gram formulation for 14 days. These short periods and a small number of participants limit what can be said about longer-term use. ^[1]

Read the bacterial and skin outcomes separately

A nonsignificant result is not proof that every possible formulation or dose would never work. It means the study did not establish a benefit for this formulation, population and schedule. The authors also noted local application-site reactions and one hypersensitivity reaction that led to stopping the study product; no serious adverse events were reported in this short trial. ^[1]

How does this fit other eczema microbiome research?

Another investigational enzyme, SA.100, also did not show a short-term clinical advantage in its own controlled trial. In contrast, studies of B244 and S. hominis A9 evaluated different approaches, outcomes and time frames. Their results cannot be transferred to XZ.700 just because all are described as microbiome research. ^[2][3][4]

The FB-401 trial and earlier Roseomonas studies illustrate another distinction: promising uncontrolled observations need a later controlled comparison. Other small studies have tested bacterial lysates, an antimicrobial fragrance and inactivated microbial extracts, with results that must be interpreted for each formulation. ^{[5][6][7][8][9][10]}

What should a patient do?

Do not try to recreate an experimental treatment at home or stop a prescribed eczema medicine. A sudden painful rash, pus, fever or rapidly spreading symptoms warrants prompt medical assessment. Research into bacteria includes laboratory and clinical outcomes; only your clinician can evaluate whether your skin is infected or inflamed and which care is appropriate. ^[12][13]

Read the wider evidence in context

Skin-microbiome research includes studies of live organisms, inactive bacterial material, proteins targeting bacteria, and ordinary skin-care products. Clinical scores, itch reports, skin barrier tests and bacterial measures do not answer the same question. Guidelines support individualized eczema care and moisturization; studies of other formulas cannot be transferred to a different product. ^{[11][12][13][14][15][16][17][18][19][20]}

Dr. Arsy #003 in a daily routine

Explore Dr. Arsy™ Hydration Recovery Moisturizer #003, 4 oz, a fragrance-free moisturizer for dry, sensitive and eczema-prone skin. The studies discussed here did not test #003 and do not show that it alters the microbiome, treats eczema or treats infection. For babies, ask the child's clinician before choosing skin-care products.

Related reading

• B244 for Eczema Itch: What the 547-Adult Trial Measured
• Staphylococcus hominis A9 and Eczema: Why a Safety Trial Was Not Proof of Clearance
• Can a Moisturizer Change the Eczema Microbiome? A 7-Day Study With 22 Analyzed
• A Nature-Derived Microbial Lotion for Eczema: Why a 28-Day Signal Needs a Placebo
• Microbiome treatments: why later trials matter
• Eczema or skin infection? Warning signs and care

Research and clinical references

1. XZ.700: first-in-human randomized endolysin study.
2. SA.100: vehicle-controlled endolysin trial.
3. B244: phase 2b ammonia-oxidizing bacteria trial.
4. Staphylococcus hominis A9 phase 1 clinical trial.
5. FB-401: placebo-controlled Roseomonas trial.
6. First-in-human Roseomonas mucosa research.
7. Roseomonas mucosa research in children.
8. Lactobacillus lactis lysate: placebo-controlled pilot.
9. Moisturizer and farnesol: skin-microbiome experiment.
10. Inactivated environmental microbial extract: pilot trial.
11. Staphylococcus aureus and eczema severity: systematic review.
12. International Eczema Council: skin bacteria and infection.
13. Infectious complications of atopic dermatitis.
14. Topical niclosamide and the eczema skin microbiome.
15. Isosorbide diesters and the pediatric skin microbiome.
16. Antimicrobial-corticosteroid combinations and skin microbiome.
17. Systemic eczema therapies and skin bacteria: pilot research.
18. Emollients and skin-barrier function: systematic review.
19. AAD guideline: pediatric eczema management.
20. AAD guideline: adult eczema topical management.

Educational information; not a diagnosis or individual medical advice. Cited researchers and organizations do not endorse Dr. Arsy products.