Daylight Photodynamic Therapy: Sunlight as a therapy

What is Photodynamic Therapy (PDT) and how is natural daylight-PDT different from conventional-PDT?

Throughout history, humans have revered the sun, worshipping it as a god as well as recognising its healing properties. Today, thanks to increased indoor living and artificial light, our relationship with our star has diminished. Yet, scientists and medical professionals alike are increasingly realising the influence it wields and using the sun’s power to improve our overall health and wellbeing. Phototherapy (Photodynamic therapy) is one area where we have rediscovered the power sunlight has to treat ailments.

The rediscovery of phototherapy and its development in modern medicine was not until the second half of the 20th century when the ancient texts were translated for the modern-speaking world.

Since then, the phototoxic reactions, created by light on human tissues under specific conditions, have been used to treat several diseases including vitiligo, psoriasis, and more recently cancerous and pre-cancerous lesions such as Actinic Keratosis.

What is Photodynamic therapy?

Photodynamic therapy (PDT) is a relatively young therapeutic modality that holds much promise for the treatment of illnesses characterised by the excessive growth of either host cells (i.e. neoplasms) or pathogens.

Going by several names such as photoradiation therapy, photochemotherapy, PDT combines a drug that makes cells sensitive to ultraviolet (UV) light. The medicine, which can be orally taken or topically applied, is called a photosensitiser or a photosensitising agent.

There are different types of sensitising medicine, and each are activated by UV light at different wavelengths. The type of drug and light wavelength you have depends on where the cancer is in your body.

How does Photodynamic therapy work?

The modern PDT is based on the local or systemic application of a photosensitive compound – the photosensitizer, which is accumulated in pathological tissues. These molecules absorb the light of the appropriate wavelength, producing a type of oxygen that leads to the selective destruction of the harmful cells. The photo-cytotoxic reactions occur only within the pathological tissues, in the area where photosensitizer medicine is distributed.

Natural daylight-PDT

Daylight-PDT is a modified protocol of the standard treatment, which is more convenient and can be less painful. This is because natural daylight on our skin is less invasive, reducing post-treatment aches, while still being effective to kill the host cells or pathogens.

Unfortunately, daylight-PDT is far less easy to control than the standard procedure of using artificial lights. One of the main concerns is the measurement of the required light intensity to activate the therapeutic process. Another is the fact that it relies on the weather, as a certain amount of natural exposure is needed.


To reduce the risks involved in natural daylight-PDT, siHealth has created an innovative mobile and web solution SmartPDT. Designed to take the worry out of daylight-PDT, SmartPDT allows for healthcare practitioners to schedule, record, and monitor patients treatment from one central portal. Additionally, through the mobile app, patients can choose when and where they have their treatment, scheduling it around the weather and UV exposure, be it within a hospital or the comfort of their own home.

To find out more about SmartPDT, click here to download the product brochure or contact our sales team for a personalised demo.

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