The Herbivore Blue Tansy Resurfacing Clarifying Mask (£38) is one of the brand's best-selling products in the US, and this month, it finally comes across the pond via Cult Beauty. Why's the mask so popular? The formula — using plant derived AHAs and BHAs — gently breaks down dead skin cells on the surface on your skin, while simultaneously clearing out clogged pores. The addition of blue tansy essential oil, which has anti-inflammatory properties, means you're left with skin that's clearer, smoother, and less irritated, with the added bonus of smaller-looking pores.