ASK A SKIN CARE BIOLOGIST

QUESTION: Why is water irritating to the skin?

— Carrie L.

Short answer: Skin’s protective acid mantle is mildly acidic (~pH 4.9–5.5). Neutral water (pH ~7) shifts surface pH upward. Repeated, prolonged exposure—especially with warm/hot water or tap impurities—can weaken barrier lipids and proteins, aggravate dryness, sensitivity, and acne-prone states.

1. pH mismatch matters. Your acid mantle inhibits pathogenic growth and supports lipid-processing enzymes. Even neutral water is more alkaline than skin and transiently raises surface pH. Chronic elevation (e.g., from alkaline cleansers) correlates with barrier dysfunction and inflammation. Keep formulas mildly acidic and water contact brief.
2. Temperature is critical. Warm/hot water increases transepidermal water loss and sebum solubility, leaving skin tight. Heat also stresses capillary-rich thin areas (periorbital) and can denature structural proteins over time. Use cool water for rinsing only.
3. Tap water impurities vary. Trace metals, disinfectants, organics, and microbes differ by region and may irritate compromised skin. If you’re actively sensitive (rosacea, barrier damage, post-procedure), rinse with cool distilled water to minimize variables and pat dry.

Practical protocol: Use a mildly acidic, non-foaming cleanser; rinse briefly with cool (distilled if sensitive) water; immediately apply anti-inflammatory hydration and seal with a non-occlusive oil serum.

See OUMERE guides/products: Sensitive Skin: The Cellular Response • Barrier Repair After Retinoid/Acid Damage • Oil Dissolution Theory® Cleanser • UV-R™ Concentrate • Serum Bioluminelle

QUESTION: Is spraying good bacteria, such as Nitrosomonas eutropha, beneficial for your skin?

— Hoda S.

Short answer: The concept is intriguing, but evidence remains preliminary and not broadly generalizable. The skin microbiome is highly individualized; successful, stable incorporation of exogenous species is uncertain, and compatibility/safety aren’t guaranteed for all skin types.

For a probiotic spray to be beneficial, all must be true:

1. It does not displace/antagonize your beneficial resident flora.
2. It successfully integrates into the existing ecosystem.
3. It contributes net protective function (e.g., reduces inflammation, supports barrier) once integrated.

• Microbiome composition is person-specific; what helps one may flare another.
• Unlike the gut, skin lacks robust acid and enzymatic “filtering,” so topical introduction of live species can irritate sensitive skin.
• Lower-risk strategy: maintain the microbiome you already have—keep pH mildly acidic, avoid fragrance/essential oils, and minimize barrier-disruptive practices. Gentle, controlled exfoliation helps normalize turnover and reduce inflammatory niches.

See OUMERE guides/products: Essential Oils Are Not Essential • No. 9 Daily Liquid Exfoliant • Acne & Inflammation: Biological Origin

QUESTION: Is moisturizer containing SPF equally protective as using a pure SPF product?

— Olivia F.

Short answer: Only if you apply the tested dose and the product is broad spectrum. Most people under-apply moisturizers or foundations, delivering far less than the labeled SPF.

• Dose: ~1/4 teaspoon (~1.25 mL) to the face alone is needed to approximate labeled SPF.
• Broad spectrum: Ensure protection across UVA (aging) and UVB (burning). Many cosmetics tout SPF yet lack robust UVA coverage.
• Best practice: Use a dedicated, broad-spectrum sunscreen as your final daytime step; treat SPF in moisturizer/foundation as a bonus, not your primary shield.

See OUMERE guides: The OUMERE Routine (daytime layering with SPF)

References

• Grice, E. A., & Segre, J. A. (2011). The skin microbiome. Nat Rev Microbiol, 9(4), 244.
• Lee, N. Y., et al. (2018). Nitrosomonas eutropha spray for keratosis pilaris: randomized trial. J Drugs Dermatol, 17(3), 285–288.
• Stettler, H., et al. (2017). Panthenol emollient: moisturization, barrier restoration, microflora effects. J Dermatol Treat, 28(2), 173–180.
• EPA. National Primary Drinking Water Regulations. epa.gov
• Anjaneyulu, L., et al. (2012). Defluoridation & rainwater harvesting using solar still. Ind Eng Chem Res, 51(23), 8040–8048.