Photodynamic Therapy (PDT) is used as a skin cancer treatment, a term which describes the application of a photosensitizing chemical to a specific skin lesion or an area of skin which, when followed by exposure to visible light results in activation of the photosensitizer.
Once this photosensitizer is irradiated and activated by an appropriate light source, reactive oxygen species (“singlet Oxygen”) are produced which damage subcellular structures in the cells involved leading to their destruction (called phototoxic effect).
The photosensitizer most commonly used in dermatology is 5-aminolevulanic acid (5ALA).
When 5-ALA is applied to the skin it is absorbed faster by the more rapidly dividing, abnormal cells such as skin cancer and pre-malignant skin cells, keratoses, acne and rosacea lesions, bacteria within acne lesions, psoriasis, warts.
This leads to a larger and more rapid accumulation in these cells of the photosensitive substance Protoporphyrin IX. When this is irradiated by light of the correct wavelengths, it gives off the energy which results in the destruction of these abnormal cells.
Normal skin cells remain relatively unaffected.
It is the preferential absorption of 5-ALA by the abnormal, proliferating or hyperactive cells which forms the basis of photodynamic therapy in dermatology.
Cosmetic Applications of Photodynamic Therapy
In the process of treating thousands of patients for severe sun damage and skin cancers, it was observed that PDT also resulted in a more generalized, marked improvement in a wide range of other, less severe but very common features of sun damaged skin. These include:
- Actinic Keratoses (scaly dry sun-spots)
- Dyschromia (mottled hyperpigmentation / freckles)
- Telangiectasia (facial and chest blood vessels / “spider naevi”/ “spider veins”)
- Fine wrinkling
- Uneven or damaged skin texture
These observations have led to the use of PDT for a range of cosmetic improvements to sun damaged and ageing skin (Photorejuvenation).
As well, PDT is proving very effective for other cosmetic skin problems such as acne, rosacea, sebaceous gland hyperplasia, warts, psoriasis and seborrheic keratoses (senile warts).
How many treatments are required?
Most people need only one or two treatments however, depending on the amount of damage, and the thickness of the lesions, more treatments may be required.