Psoralens and PUVA (Ultraviolet Light) Therapy for Psoriasis

Ultraviolet therapy has been widely used for psoriasis for almost a century. Ultraviolet B (UVB) is beneficial for psoriasis but the treatment should be managed by a medical doctor as the risk for skin cancer in the long term is always a consideration. In countries with limited facilities, patients still resort to sunlight exposure but modern techniques with UVB lamps are a better and safer option.

Psoralens and PUVA therapy are often used as a phototherapeutic (light therapy) option for patients with psoriasis. These treatments should be managed by a dermatologist with the appropriate equipment and facilities. Here a special chemical known as psoralen is exposed to UVA and it helps ease the skin thickening which is a characteristic feature of psoriasis.

What are psoralens?

Psoralen is a natural chemical found in many plants and it is highly sensitive to ultraviolet light, particularly UVA. It affects the DNA strands in the skin cells and can be taken orally or used in a bath before UVA exposure. Psoralen is found in the Psoralea corylifolia plant, which is also known as the babchi plant in Ayurvedic medicine. It may also be found in varying concentrations in other plants like figs, celery and parsley.

How does PUVA and Psoralens work?

Before UVA exposure, psoralens will be taken orally or applied in a bath. Psoralens, when activated by UVA, will cause the DNA in your skin cells to cross link. This prevents cell replication and in psoriasis, where hyperproliferation (fast and excessive skin cell replication) of the skin is the problem, this effect of psoralens can be beneficial. However, psoralens and PUVA treatment cannot be continued indefinitely as it may increase the risk of certain types of skin cancer.

Is PUVA treatment effective?

PUVA treatment is very effective especially in patients where the thickened skin plaques are not resolving with other psoriasis treatment options. It should only be done at an approved facility where a dermatologist and other health care workers can supervise the treatment.

PUVA is sometimes used for eczema and vitiligo with varying success. It is most effective for psoriasis.

How long does PUVA take to work?

Most patients who experience relief from PUVA treatments report an improvement within 5 to 8 weeks. In most facilities, PUVA treatment will not be continued past 8 weeks. Many patients who will benefit from PUVA report a complete clearance of the psoriasis skin lesions and others do report about a significant improvement even if there is not complete resolution. Some psoriasis sufferers do not experience significant relief and this is usually because they were not good candidates for PUVA treatment. This is why PUVA therapy should always be supervised by a dermatologist who is well versed with the treatment.

You may need 2 to 5 treatments per week and you will have to stand in the booth for a few seconds to several minutes. Treatment may extend for 5 to 8 weeks. Individual doses of psoralens, length of UVA exposure and frequency of treatments varies for patients and the dermatologist will have to assess your individual case before commencing the PUVA treatment.

What are the side effects of PUVA?

Like many therapeutic options, there are side effects but most of these are only dangerous if you continue on PUVA treatment for too long and if it is not supervised by a medical practitioner. Some of these side effects include :

  • Increased risk of skin cancer.
  • Premature aging.
  • Darkening of the skin.
  • Dryness and itching of the skin.
  • Skin redness and burning sensation.
  • Damage to the eye (example : cataracts) if you are using oral psoralens – your dermatologist will provide you with a special type of sunglasses to block out UVA as psoralen deposits in the eye may react to sunlight.

Is PUVA treatment expensive?

PUVA treatment can be costly, especially if your medical aid does not approve the therapy or if you dermatologist is not contracted into medical aids. Many patients opt for PUVA treatment while they holiday abroad as it may be cheaper but you should be cautious about undergoing PUVA treatment in some countries. The therapy may not be as closely regulated and may be conducted by untrained staff. This can increase the chance of side effects.

PUVA should not be confused with other types of ultraviolet light therapy and home devices which are sometimes sold as psoriasis ‘cures’  but may have no therapeutic value.