In-vitro vs in-vivo testing: Which method judges SPF the best?

Ria Bhatia
Jan 08, 2026, 06:58 AM

The dubiety associated with sunscreen

Claims about SPF (Sun Protection Factor) pasted bold and clear on the packaging labels are often rigged or exaggerated.

Testing SPF in sunscreen

A sunscreen's SPF can be measured via two methods: in-vitro (in a laboratory) and in-vivo (on human skin).

The new legal mandates

In November 2025, the Bureau of Indian Standards (BIS) was forced to revisit the traditional methods of SPF approvals, when controversies took over social media.

In-vitro vs in-vivo testing

While in-vitro is a fast, cost-effective method, the catch is that artificial skin does not replicate human skin precisely, says Dr Madhuri Agarwal.

Why is in-vivo testing favoured?

In-vivo testing is considered ideal by most regulatory authorities for it tests on real skin, and measures real-life results.

How to choose the right sunscreen?

Choose sunscreens that specifically mention testing under ISO standards (ISO 24444 for SPF, ISO 24442 for UVA protection). In India, check for BIS certification, if available.

Read through the fine print

Don’t assume that a higher SPF automatically gives you significantly more protection. For instance, SPF 30 blocks around 97 per cent of UVB rays, SPF 50 offers about 98 per cent, and SPF 100 covers roughly 99 per cent.