Topical photodynamic therapy (PDT) is a treatment for some types of superficial skin lesions.
It uses a drug, methyl-aminolaevulinic acid, contained in a cream. The drug does not have a direct effect but is converted in the skin to another compound, which is sensitive to light. Red light is then shone on to the area to activate this compound and eliminate the skin lesion. One of the important advantages of this treatment is that it damages the abnormal areas whilst preserving normal tissue, resulting in better healing and generally, a good cosmetic result.
Before you attend for treatment
If your lesion is crusted or thickened, please apply Vaseline petroleum jelly to the area, twice daily for 14 days, before your appointment. This will help to soften the surface of the lesion.
What does the treatment involve?
When you attend the Photodynamic Therapy Clinic, the treatment will be discussed fully with you and you will be asked to sign a consent form. Any crust or scale will be removed and the cream will then be applied to the lesion, and covered by a dressing. After 3 hours, red light is shone onto the area. The light reacts with the light sensitive compound. Usually, a mild tingling or burning sensation is experienced. This discomfort is reduced by the application of cooled air to the lesion, during the light exposure. Very occasionally, you may require a local anaesthetic. At the end of the treatment, the area will look red and possibly, swollen. You will be asked to cover the area with a dressing for a few days after treatment. The area can then be left exposed but kept clean. The lesion will behave like a very superficial burn with mild discomfort for up to 5 days and oozing or crusting, lasting up to 14 days. This will then dry to a scab, which will fall off naturally. Most patients require two treatments, 1 week apart. You will be seen again in clinic, 3 months later to ensure you have responded to the treatment. A minority of patients require a second treatment at that stage.
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After the cream has been applied to your skin, you are free to leave the hospital; however, you must return to the department at the time we tell you for the light phase of your treatment.
After treatment
- Avoid any injury, rubbing or scratching of the area until the skin has fully healed. Leave any scale or scab to separate naturally.
- You can wash, bath or shower as normal but again, avoid injury, rubbing or scratching and gently pat the area dry.
- If the redness and swelling persists, or if there is excessive crusting or weeping, this may be a sign of infection and antibiotics will be required. These can be obtained from us or your own doctor.
- In most patients, the area heals quickly with an excellent cosmetic result but there is a small risk of loss or increase in pigmentation in the skin. Ulceration, scarring and allergic reaction to the cream are extremely rare side-effects.
Storage of results
We record the information about your treatment on a secure database for audit purposes in accordance with good medical practice. The anonymised data may also be used for research.
If you have any queries about your treatment or problems after the treatment, please contact the Department of Dermatology.
Contact details
Chapel Allerton Hospital
Alison Wood, Nurse Practitioner, Phototherapy Department
(or contact your own doctor)
