Photodynamic therapy

A review carried out in 2008 considered the various uses for photodynamic therapy (PDT) including its potential role in the treatment of acne (Morton et al., 2008). PDT is a type of light therapy in which a photosensitising drug is applied to the skin and then a light source is shone onto the skin in order to alter, in some way, targeted cells. The light source varies and can be a laser, filtered xenon arc and metal halide lamps, fluorescent lamps and light emitting diodes. When used for treating cancerous lesions, for example basal cell carcinomas, the process of applying the light to the sensitised skin is to kill the cancer cells. In acne treatments, the exact mechanism is not wholly understood but it is thought that the treatment has a number of effects:

1. It has an antimicrobial effect on P. acnes.
2. It causes selective damage to sebaceous glands.
3. It reduces the keratinocyte shedding and therefore follicular blocking.

A number of studies are reported by Morton et al. (2008) showing beneficial results from PDT both immediately after treatment and at various time points after the treatment. Some studies looked at results after one treatment, others after a series of treatments. Some of the studies reported some unpleasant side effects including pain during treatment, severe erythema after treatment, pustular eruptions and epithelial exfoliation. Most of the studies were small. Few trials compare laser light therapy to conventional treatments but in one case where PDT was compared to 1% adapalene gel the results showed that PDT was no better than the gel (Hamilton et al., 2009). The conclusion drawn by Morton et al. (2008) was that whilst this looks like a promising treatment for inflammatory acne on both the face and back, further work needs to be done on determining the most effective treatment protocols.

A Cochrane review looked at the evidence in relation to laser therapy and found that trials of blue light, blue–red light and infrared light were more successful than light alone particularly when multiple treatments were used (Hamilton et al., 2009).