Treating Psoriasis with Light Therapy

Light therapy or known as ‘phototherapy’ is one of the recommended treatments to improve the symptoms of psoriasis. However, light therapy does not cure psoriasis, but helps to manage the condition and improve the quality of life. It involves shinning ultraviolet (UV) light on the skin which can remedy skin inflammation and reduce the itchiness, red patches associated with plaques. Light therapy works by slowing down the excess growth of skin cells and limits the plaque formation.

Treatment is based on the severity of psoriasis at the time of presentation. Mild psoriasis (3 – 10% of the body) is usually treated with topical therapy and progressing to light therapy in the case of insufficient response. In fact, light therapy is suitable for moderate to severe psoriasis (> 10% of the body) as recommended by doctors.

There are 2 main forms of UV light used in the treatment:

• Ultraviolet Light A (UVA) has a longer wavelength and can penetrate to deeper levels of the skin in combination with psoralen which makes the skin more receptive to the UVA
• Ultraviolet Light B (UVB) has a shorter wavelength and reaches the upper levels of the skin, and does not require psoralen

Although both UVB and UVA are found in sunlight, it is not recommended for everyone as it is not as effective for the treatment of psoriasis as prescription phototherapy.

Psoriasis responds to UV radiation favourably. However, the underlying mechanisms are not well understood. It is generally accepted that UV light induces apoptosis (cell death) of pathogenic T cells and keratinocytes, leading to local and systemic immunosuppression. In short, light therapy stops the overproduction of skin cells either by damaging their DNA or by stopping the cells from dividing by “locking” the DNA and also suppresses the skin immune system.