Acne light therapy is also known as acne light treatment, phototheray, photolight therapy, photodynamic therapy, or even blue light therapy. All titles refer to the use of light as a treatment for acne. This is not a new idea. For some time it has been known that sunlight improves the skin of those suffering from acne, unfortunately the harmful UV rays can also cause skin cancer. After finding that artificial UV rays were not as effective as sunlight the relationship between acne and light was studied more closely.

Scientists and Dermatologists discovered that certain visible violet light within sunlight, ranging from 405 to 420 nm, activates a porphyrin, which is a part of the acne-causing bacteria called Propionibacterium Acnes (P. acnes). When the porphyrin is activated it releases singlet oxygen, thereby damaging and killing the bacteria. In essence the acne bacteria self-destructs.

More good news is that this range of light waves falls just outside the ultraviolet spectrum and will therefore cause little, if any, skin damage. In fact most treatments are followed with the application of red light waves, which have been shown to increase the skin's healing processes. After just 3 consecutive days, light treatments have been shown to safely reduce bacteria in the pores by 99.9%.

These treatments are usually created by fluorescent lamps, high-intensity LEDs or dichroic filament bulbs. Dermatologists tend to use higher powered lights which may cause slight redness or drying of the skin, especially in the beginning of treatments. Some light therapies have been developed and modified for at-home use. Such lights are more gentle than clinical treatments and so have a smaller chance of causing irritation.