What is Psoriasis?
Psoriasis is a common skin disease that looks like eczema. It looks like a shiny, red scale or plaque that is thick and can occur in one or two lesions or can be found on the scalp, nails or across the entire body. They can be very itchy and cause very bad dandruff or flaking of the scalp.
What causes Psoriasis?
Psoriasis is an abnormal relationship between the immune system and the skin. Due to some trigger (such as the wrong bacteria in the gut stimulating the immune system), immune cells move to the skin and stimulate a reaction.
Once a person has psoriasis, often it is made worse if somebody has trauma to the skin. That might be from scratching or even sunburn. Some people also describe stress as making it work or certain foods.
What are some of the treatments?
Simple treatments include avoiding triggers such as trauma, stress or sunburn and then escalating to topical creams like steroids or Vitamin D creams (Daivobet). If psoriasis is really bad, it might be helpful to treat any underlying gut health issues and vitamin deficiencies such as vitamin D to settle down an abnormally active immune system.
Another therapy is UV light treatment, which involves exposing the psoriasis to certain wavelengths of light. These help change the behavior of the immune cells in the area and stimulate recovery.
When to use a UV light to treat psoriasis?
Sometimes, there are too many lesions to use topical treatments or the topical treatments do not work. In these cases, the use of UV light therapy has been shown to be effective. The wavelength of UV light is just below blue light in the electromagnetic spectrum occurring between 290-400 nm. Special lamps that deliver UV light at certain doses have been shown to be effective at treating psoriasis.
What kind of UV light is used and what machine is used?
There are several kinds of UV light used; this is called UV phototherapy. Narrow Band UV therapy, NB-UVB, is commonly used and uses a wavelength between 308- 313 nm (most devices on the market use 311nm). There are broadly two kinds of devices; a handheld wand or a whole body machine similar to a tanning bed.
A handheld device delivers higher doses targeted to small plaques for people with discrete lesions (such as the scalp) whilst a whole body device for those with diffuse disease. Many patients will have both devices and start with the whole body machine and then use the handheld for lesions that bother them.
What dose do I use?
The dose of therapy to use depends on the skin type. Fair skinned individuals, termed Fitzpatrick I will start at 130mJ for 15 minutes, three times per week for 20-30 sessions (about 6-8 weeks pending a response) whilst
darker skin will need more, perhaps up to 400mJ. There are dose regimes available from the manufacturer, your dermatologist or by looking for a reputable online guide. In general, the dose is chosen by testing it on a piece of psoriasis rather than normal skin; if effective, then it can be used.
How useful is UV Phototherapy?
For severe psoriasis cases, a 75% reduction in disease has been found after 8 weeks at an appropriate dose. In general, the dose is escalated to what the skin can tolerate. Psoriasis is not just treated by UV therapy alone, there are unique drugs that can be taken to help people that affect the immune system.
What are the side effects of UV therapy?
UV light can damage the skin. It can cause redness, blistering and pain. This means that the dose is too high and it needs to be reduced. The skin can accommodate a higher dose over multiple sessions and so the dose can be increased (the mJ or strength) however if there is a gap in treatment, more than 2 weeks, it should be halved. If the gap in treatment is 4 weeks, you should start from the minimum dose. Journal articles state that there is no skin cancer risk from UV therapy.
How to protect myself from the side effects and risks?
All patients should aim to put broad spectrum (not just SPF 50) sun cream over the non psoriasis areas prior to therapy to protect from UV DNA damage and should wear UV protecting goggles (not just sun glasses) to protect their eyes. It should be noted that scientific articles suggests there is no damage to the eyes. If there is psoriasis on the eyes, a small dose can be trialled. Patients should moisturise immediately after the treatment and twice daily. You should cover the genitals unless instructed to by a doctor.
Is laser, LED or lamp more effective?
There is debate in the literature regarding phototherapy more broadly about whether LED, lamps or Lasers are superior. So far, there is no indication that one is better and all forms have been associated with improvement. For example, some research shows that blue light is effective against psoriasis and is near UV in the electromagnetic spectrum. Furthermore, research shows LED to be effective as well as laser. Natural sunlight has been shown to improve psoriasis. Patients should aim to find a device suitable to them, learn to use the device starting at an appropriate dose and then avoiding side effects.
REFERENCES:
Nakamura M, Farahnik B and Bhutani T. Recent advances in phototherapy for psoriasis F1000Research 2016, 5(F1000 Faculty Rev):1684 (doi: 10.12688/f1000research.8846.1)
Singh et al The Patient’s Guide to Psoriasis Treatment. Part 1: UVB Phototherapy. Dermatol Ther (Heidelb). 2016 Sep; 6(3): 307–313.
Published online 2016 Jul 29. doi: 10.1007/s13555-016-0129-2
