MAL-PDT using natural daylight has the benefit of being less painful whilst being equally effective. Treatment can be undertaken during spring, summer or autumn in Taranaki.
The natural daylight PDT procedure is as follows:
- To improve efficacy, patients can be using a peeling cream for 10 days or so prior to treatment (eg urea cream).
- A suitable day is selected for treatment; overcast with temperature over 10C is best. In most parts of the world, treatment can be undertaken year-round during office hours. Rainy days are unsuitable.
- The skin to be treated is gently washed.
- A clear sunscreen is applied to all skin to be exposed to daylight including intended treatment area (it can also be applied after the treatment cream)
- The field to be treated is marked out
- Scale and crust are lightly scraped off
- Methyl aminolevulinate cream is applied to the field. One to two grams (one tube) will treat the entire face.
- No more than half an hour later, the patient should go outdoors to expose the treated area to daylight. Delay in exposure leads to greater pain.
- If it is sunny during summer, stay in a lightly shaded area. If it starts to rain, move to an outdoor shelter exposed on 3 sides.
- Sit quietly during the session, rather than taking exercise, as sweat will reduce the penetration of the medication.
- Two hours later, the cream is washed off using saline.
- Remain indoors for the rest of the day. If it is essential to be outdoors, reapply broad-spectrum sunscreen and/or cover-up.
Natural daylight PDT is followed by sunburn-like inflammation in treated areas for 5 to 8 days. The skin is red, and may become blistered and crusted. The reaction tends to be most severe at 3 to 4 days after treatment. Redness can be reduced by pre-treatment with topical steroid.