The Day Defence SPF25 uses a Zinc Oxide mineral sun filter to provide sun protection. The Zinc Oxide is present in a very high percentage and forms a significant part of the product. The Day Defence SPF30 uses a chemical sun filter and does not use Zinc Oxide for sun protection.
However, the SPF30 does contain Zinc Oxide as an ingredient. Although it is in much smaller and different format. It is present as we really like the effect of Zinc Oxide as an anti inflammatory ingredient. So while it is not a main ingredient we know that Kalme customers like the effect from the SPF25 so we have included it.
I hope this explains the difference.