As consumers, 19.3% of us have experienced a skin reaction to a product in the last month and 37% of us have avoided using skincare products due to previous flare-ups.* So imagine how it feels as a new parent to start putting creams and lotions on your newborn’s precious skin for the first time. No other area of beauty attracts such agonised decision making; sleep-deprived parents pore over labels and worry about the slightest rash or spot.

That’s why we selected babycare as priority area for validation when we developed our new XtraMild in vitro test for skin mildness. Mildness claims must be substantiated with the best evidence available, and any test method that reduces the need for human trials in this sector is especially welcome.

How to assess mildness in already-mild babycare products

We carefully researched the UK’s bestselling products in several babycare categories: washes, shampoos, sunscreens, moisturisers and oils. Each product was applied to the surface of the skin models for 5 time points ranging from 1 to 48 hours, and we measured the impact on the health of the skin cells. The results were expressed as the ET50 value – the time taken to reduce the viability of the skin cells to 50% compared with untreated controls.

Without the reference database, the significance of the ET50 would be very difficult to interpret, so it was essential to have benchmark values for comparison. Once the benchmarks are available, ET50 values then provide a way to place the results into a rank order of mildness potential. For additional information, each product was assigned an irritancy classification based on the initial validation of the standard ET50 test ranging from “non irritating” for the mildest through to “strong/severe” for the most irritating.


As expected from the INCI lists for the product types, the study confirmed that the rank order of the product groups in terms of irritation potential (from most to least irritating) was:

Washes > shampoos > sunscreens > moisturisers > oils

Shower gelSurfactant-containing products had the greatest skin impact: washes and shampoos all caused some degree of irritation but there was approximately a 3-fold difference between the four leading brands for both types of product, ranging from a “very mild” to “moderate” irritancy classification.

Four leading baby sunscreens, all SPF50+, showed big differences in mildness, with the least mild having an irritation potential comparable with a shampoo (but still classified as “very mild”) while the mildest had no impact even after 48 hours.

All of the 4 moisturisers were classified as “non-irritating”. One showed some irritation potential relative to the other three; this product, unlike the others tested, was a lanolin-containing formulation specifically designed to prevent nappy rash. The baby oils, as expected with simple formulations were “non-irritating”.

The results demonstrated that the new XtraMild test can detect even subtle differences in very mild formulations, allowing brands to provide credible, science-backed reassurance to parents and carers when selecting a product for their baby.

Further applications for mildness testing

We’ve also assessed a wide range of adult cosmetic and personal care product types including shampoos, face masks, soaps and facial washes. We will continually build this unique database, including leading products in different international markets, providing a powerful way for our client companies to assess the mildness of their formulations and how they stack up against anonymised values across industry.

Find out more here, or get in touch if you’re interested in benchmarking your own ingredients or formulations.


*Naldi et al (2014). Prevalence of self-reported skin complaints and avoidance of common daily life consumer products in selected European regions. JAMA Dermatol 150(2): 154-162