iD Active Cartridge Concentrate Irritation is an active concentrate meant to be used in combination with a Clinique iD base. This unique green cartridge contains a high concentration of lactobacillus probiotic ferment, which soothes irritation and redness on both sensitive and reactive skin. After just one application, your skin will feel instantly more comfortable; after one week, it will be significantly less irritated. And the best part? Once you've used up an entire bottle, your skin will also be visibly less red.