WHEN IT GOES WRONG: When external irritants like pollution or everyday impurities remain on skin’s surface, it’s thought that these impurities can trigger the Defense Barrier to signal skin’s immune responses to fight off foreign invaders. This is sometimes enough to be seen as red irritation or red blotchiness, but even if you can’t see it immediately, the long-term effects are still affecting skin’s healthy look. In addition, particles or excess sebum left on skin can cause blocked or enlarged looking pores.