Phototherapy simply means treatment with light. For treating skin disease, Narrowband ultraviolet B (UVB) light is the most common type of phototherapy. This uses a special machine to emit UVB light at 311-312 nm, which is the most beneficial portion of natural sunlight for skin diseases. Importantly, it also avoids the UVA aspect of sunlight which is very damaging to skin, and can accelerate aging and progression towards skin cancers.
Broadband UVB phototherapy (290-320 nm), PUVA (Psorlaen and UVA), and UVA1 (340-400 nm) are other forms of phototherapy that are used less frequently in treating eczemas, but may be used in certain circumstances.
Phototherapy appears to work in several ways:
While it is very safe and is arguably safer than even natural sunlight due to it’s more specific and controlled nature, it still can cause burns, increased aging, and increased risk of skin cancers over time.
Phototherapy is used for widespread eczema or for localized eczema (such as hands and feet) that has not responded sufficient to topical treatments. For some, it can be a way to avoid using more powerful systemic treatment such as cyclosporine or methotrexate.
Yes, it seems to help about 60-70% of patients with eczema that have not responded adequately to topical treatments, though it does not work for everyone. When it does work, it is not a rapid improvement like some treatments: generally 1-2 months of steady treatment is necessary to start to see improvement. Fortunately for many patients, when it does work it seems to be a “remittive” therapy, meaning it can put the eczema in a quiet state for a longer period of time, sometimes even long past the phototherapy has ended.
There are several issues with phototherapy that must be considered before starting treatment: