ALA(Amino Levulinic Acid) is a photosensitizing agent used in conjunction with red light activation. It is highly effective at removing sunspots from the head,arms and hands. It reacts to the PDT light treatment to create molecular oxygen which gets rid of sun damaged and pre-cancerous sunspots.

Metvix is also a photosensitizing agent used in conjunction with PDT. It is also highly effective for removing sunspots. It is also the most effective treatment for thin Basal Cell Carcinomas and Bowens Disease.

Below is a comparison table showing their various strengths: