The Water Resistance SPF Laboratory Test In Vivo is a standardized clinical evaluation performed on human volunteers to measure the actual Sun Protection Factor (SPF) of sunscreen formulations and verify their water resistance properties. This test provides regulatory-compliant data for labeling and marketing claims related to sun protection efficacy and durability after water exposure.

Purpose of the Test

The purpose of this test is to determine the protective effectiveness of a sunscreen product against UV-induced erythema (sunburn) and to confirm its water resistance claim. It supports regulatory and marketing claims such as the SPF factor and “Water-resistant”  in compliance with ISO 24444:2019 and ISO 18861 standards.

How the Test Works

This In Vivo involves controlled exposure of the skin to UV radiation before and after sunscreen application, both under dry conditions and following defined water immersion cycles. The test determines the ratio of the minimal erythema dose (MED) on protected versus unprotected skin, producing the SPF value. Water resistance is assessed by repeating measurements after immersion, ensuring that the product maintains effective protection even when exposed to water.

Testing Standards

• ISO 24444:2019 — In Vivo determination of the sun protection factor (SPF)
• ISO 18861 — In Vivo determination of water resistance of sunscreen products

Applications in Cosmetic Testing

• Verification of SPF values for sunscreen and daily protection products
• Validation of water-resistant or very water-resistant labeling claims
• Assessment of product durability under real-life usage conditions
• Regulatory compliance for EU and international sunscreen product registration
• Support for marketing claims such as “long-lasting protection” or “tested water resistance”

Test Procedure

1. The test is performed under controlled laboratory conditions following ISO 24444:2019 and ISO 18861 protocols.
2. A defined amount of sunscreen is applied to specific skin areas on human volunteers.
3. The unprotected and protected areas are exposed to calibrated UV radiation.
4. Water resistance is evaluated by immersing the treated skin areas in water for a specified time, then repeating UV exposure.
5. Minimal erythema doses (MED) are determined to calculate SPF and water-resistance retention ratios.

Results & Reporting

The final report includes:

• Test protocol and compliance statement (ISO 24444:2019 + ISO 18861)
• SPF value (Sun Protection Factor) and water resistance evaluation
• Volunteer test data and statistical analysis
• Interpretation of protection efficacy and retention after immersion
• Documentation suitable for regulatory, labeling, and marketing use

Why This Test Matters

Consumers expect reliable protection from UV damage during swimming, sweating, or prolonged sun exposure. The Water Resistance SPF Test provides scientifically validated evidence that a sunscreen maintains its protection even after contact with water. Compliance with ISO standards ensures internationally recognized results suitable for product registration and labeling across global markets.

Sample Requirements

• Sample size: 300 mL of finished product
• Number of volunteers: according to ISO 24444:2019 (typically 10–20)
• Product type: sunscreens, day creams with SPF, or body lotions with UV protection
• Storage: room temperature, away from direct light unless otherwise specified

Test Parameters

• Protocol: ISO 24444:2019 + ISO 18861
• Duration: 40 days (including preparation, testing, and reporting)
• Measurement: In Vivo SPF and post-immersion water resistance
• Analysis: Statistical evaluation of SPF consistency after water exposure
• Sample quantity: 300 mL

Turnaround Time

The typical turnaround time for this study is approximately 40 days, depending on volunteer scheduling and weather or light conditions suitable for UV exposure testing.

Deliverables

• Full laboratory report in PDF format
• SPF and water resistance values with interpretation
• Statistical summary and compliance with ISO protocols
• Certificate of analysis suitable for product registration and labeling

Compliance & Standards

The Water Resistance SPF Laboratory Test In Vivo is performed under strict adherence to Good Clinical Practice (GCP) and in full compliance with ISO 24444:2019 and ISO 18861 international standards. All procedures are carried out by trained professionals in accredited facilities to ensure scientific accuracy and reliability.