Limitations of In Vivo Testing

February 22, 2026

The ISO 24444 method has underpinned global sunscreen regulation for decades. However, reliance on human erythema (sunburn) response introduces variability and ethical complexity that the industry is now actively addressing.

What Drives Inter-Laboratory Variability?

Variability in ISO 24444 testing is the cumulative result of multiple inherent features of the method. Key drivers include:

Human Biological Variability: Erythemal response varies between individuals and even within the same individual over time due to hydration and environmental influences.
Small Panel Sizes: The standard requires a minimum of 10 subjects. Small cohorts mean that one outlier response can significantly influence the final mean SPF.
Subjective Assessment: Determining the “first perceptible redness” introduces human subjectivity, which can be influenced by lighting conditions.
Equipment Calibration: Minor differences in solar simulator output, even within allowed tolerances, contribute to divergent outcomes.

Ethical and Inclusivity Limitations

Beyond scientific variability, the current testing standard presents significant ethical considerations:

Skin Type Exclusion: Testing is primarily conducted on individuals who burn easily. This excludes darker skin tones, leading to a lack of direct efficacy data for significant portions of the population.
Induced Skin Damage: The test intentionally induces a mild sunburn response on volunteers, which is increasingly viewed as undesirable from an ethical standpoint.

The Movement Toward In Vitro Methods

The industry is moving toward validated in vitro (laboratory-based) SPF testing. These methods offer potential advantages such as reduced biological variability, greater reproducibility, and no reliance on inducing sunburn. The TGA has already signaled interest in these modern pathways.

Wild Child Laboratories stays at the forefront of these regulatory evolutions, ensuring our partners are prepared for future shifts in SPF standards. Partner with us to stay ahead of the curve in sunscreen innovation.

Frequently Asked Questions

Yes, our minimum order quantities (MOQs) are a function of the calibrated weights of our mixing vessel and the capacity of our filling lines. Depending on the unit size of the final product the MOQ will typically be around 10,000 units.

We do not have a product catalogue. Products will be suggested by our Product Development team based on the information you provide through the new product enquiry form.

Yes, with a better understanding of your product requirements we will develop a lab sample(s) for your review and ultimate approval. Depending on level of customisation or development required, this service may incur a fee.

Typically, 12 – 14 weeks from the placement of purchase order and payment of the deposit. Please note, the manufacturing lead time is dependent on the availability of the raw materials and packaging components, which can be confirmed prior to the placement of your order.

No, all our pricing is EX WORKS. Whilst we do not provide freight and distribution services, we can assist with the freight quotation and booking from our Facility.

Upon placement of purchase order, a 50% deposit is required, and balance is due prior to the release of the finished goods.

Yes, we can provide packaging options based on formulation compatibility and compliance standards. Alternatively, clients can provide their own packaging with the understanding that it must be compatible with our equipment and meet compliance standards.