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Photodynamic Therapy

Photodynamic therapy involves the use of a light-sensitive chemical called a photosensitiser which on its own is inactive.

When light of a certain wavelength (usually red light) shines on to the skin to which the photosensitiser was applied before, the photosensitiser is activated. The oxygen that is released by this activation kills the abnormal cells in the area that is being treated. Only the area of skin exposed to the light source will be affected and inflamed. After the inflammation settles over a few weeks, the area will clear and the lesion will have been treated.

What is the Benefit of Photodynamic Therapy?

It is used where surgery or other forms of treatment may not be appropriate.  For example, if the basal cell carcinomas are very large where surgery would be difficult or on the lower leg where skin healing is often delayed. It is also a good option where there are multiple lesions over a larger patch of skin.

Who is Photodynamic Therapy suitable for?

PDT can be used to treat various skin conditions including:

The below reasons might prevent you from having photodynamic therapy:

  • PDT is not recommended if you are pregnant.
  • The PDT cream may contain peanut oil, so tell your doctor and nurse if you are allergic to peanuts.
  • PDT is not recommended if you have porphyria (a light-sensitive disorder, where the patient is producing the same photosensitiser used in PDT and is present in the blood, skin and other tissues of the body).

What is the process of Photodynamic Therapy?

Photodynamic Therapy (PDT) is an outpatient procedure and is done by your doctor or nurse. It is a two-step treatment that is carried out 3 hours apart on the same day.  The first step is to apply a cream containing the photosensitiser to the area that needs to be treated. If necessary, any loose scale or crusts are removed first. A dressing is then applied over the cream and you will be asked to return in about 3 hours. This wait is to allow the photosensitiser to be absorbed and to convert into the active chemical by the skin.

The cream is then wiped off on your return 3 hours later and the area cleaned. A bright coloured light is then shone onto the treatment area for approximately 10 to 45 minutes (the precise time will be determined by your doctor or nurse depending on the light source).



After the treatment has been completed, a dressing will be applied for a minimum of 2 days, to prevent any further exposure to light. The area can feel hot and sore whilst it is being treated.



What are the Risks and Complications of PDT?

The short-term side effects of phototherapy include:

  • Pain. When the red light is shone onto the skin, the treated area may hurt. If it is too uncomfortable, your doctor or nurse may suggest pausing treatment for a while, or a local anaesthetic injection may be recommended. After completion of treatment, discomfort and itching may last for a few days and may require painkillers.
  • Inflammation. The treated area may initially become pink and puffy, and may ooze a little: this is a normal reaction. It settles within a few days.
  • Blistering and ulceration. The treated area may occasionally blister or ulcerate.
  • Infection. If the treated area becomes red, swollen and painful, an infection may have developed, and you should contact your doctor.

 Potential long-term side effects of phototherapy include:

  • Scarring. There may be some scarring after PDT.
  • Colour change. The skin may become darker or paler after PDT.
  • Treatment may not be effective, or the condition may come back again. If this happens, you may be offered further PDT or an alternative type of treatment may be recommended.

What is the Recovery Time and Outcome for PDT?

Your doctor or nurse will explain how you should care for the treated areas. It is usually advised that, after the dressing has been removed, you can wash, bathe or shower as usual. Do not rub the treated area, but gently pat it dry. Within a few days, a scab will form, and healing will take several weeks (depending on which part of the body was treated). Care must be taken not to scratch the area or accidentally dislodge the scab during the healing process. The use of a suitable sunscreen (SPF 30) following the procedure, especially during outdoor activities, is essential.

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