P. acnes is the bacteria that causes acne, and it is known to produce a large amount of porphyrins within the bacterial cell.

These porphyrins can be photosensitized with blue light to create an oxygen molecule. P. acnesis an anaerobic bacteria, which means it can not live in the presence of oxygen.

So when P. acnes is in the presence of blue light these porphyrins create an oxygen molecule, which ends up killing the P. acnes bacteria.

Blue light has powerful anti-bacterial properties that decongest and purify acne and problem skin and help to normalize oil production. Blue light also promotes calming and relaxation.