The UVA star rating system was developed by Boots, it is not an EU requirement to have a UVA star rating. The UVA star rating system just measures the ratio of UVA protection vs. UVB protection, so if a product has a low SPF it may still have a high level of stars, not because it is providing lots of UVA protection, but because the ratio between the UVA and UVB protection is about the same.
Our UVA star rating according to the Boots system is 3 which a good level of protection and meets the EU requirements for UVA protection. As far as we know, all sunscreens that are suitable for sensitive skin and safe for people who may be prone to eczema, have achieved a 3* rating, as it has not been possible to achieve a 5* rating using ingredients that are suitable for sensitive skin and safe for people who may be prone to eczema.
It is important to look for a sunscreen that filters both UVA and UVB rays (broad spectrum), but particularly with a high SPF to block UVB rays that cause sunburn. Sunscreens with SPF 50 protect against 98% of UVB rays, whereas SPF 15 sunscreens only filters 93% of UVB rays.