What is PUVA? Psoralen and UVA Treatment for Psoriasis
PUVA is one of the many treatment options for psoriasis using ultraviolet light to reduce skin thickening and sometimes resolve plaques completely. It is not a cure for psoriasis but can be very effective in managing the active stages of this skin disease.
PUVA stands for Psoralen and UVA. It is a form of light therapy, also referred to as photochemotherapy, where the skin reacts to ultraviolet light due to the presence of psoralens within the skin cells. It has been used in some form or the other for thousands of years by the ancient Indians and Egyptians. UVB or ultraviolet B is also used in the treatment of many skin conditions including psoriasis but with psoralens treatment, it is UVA that is most effective.
PUVA is also used for the treatment of other skin conditions like vitiligo and eczema but it is most effective for the treatment of psoriasis. Not every case of psoriasis warrants the use of PUVA. It should only be considered if other forms of psoriasis treatment are ineffective as PUVA has a host of side effects.
What is Psoralen?
Psoralen (furocoumarin) is the active ingredient found in certain plants like the babchi tree or bavachee (Psoralea corylifolia) which is used in Ayurvedic medicine. It is also present in small quantities in other fruit and vegetables like figs, celery, lime and lemons. Handling these or other plants that contain psoralens and then being exposed to the sun can result in photo-contact dermatitis and this is sometimes seen in florists and crop pickers. Individual sensitivity may vary so it will not affect every person in this situation.
Psoralen is still used in its natural form in alternative medicine, like in Ayurveda, but with modern pharmaceuticals, it is available as a capsule (methoxsalen, trioxsalen, etc). Sometimes psoralen is used topically where a patient submerges in a bath containing a solution of psoralen. For smaller psoriasis plaques, a psoralen lotion or gel is used on the affected area.
What is PUVA?
PUVA treatment works by administering psoralen prior to UVA exposure. This may be done about 2 hours before with capsules or 10 minutes prior to UVA exposure with a psoralens bath, gel or lotion. Large areas of the body may be treated in a UVA light booth or only certain areas of the skin may be targeted and treated.
PUVA treatment involves 2 to 5 sessions per week for 5 to 8 weeks. Sessions may last from a few seconds to several minutes.
Psoralen and UVA Mechanism of Action
How does PUVA work?
Psoralens makes the skin cells more sensitive to ultraviolet A (UVA). It causes the DNA strands to cross link when exposed to UVA. This cross linking prevents cell replication and is useful for conditions like psoriasis where hyperproliferation (excessive skin growth) is one of the key features of the disease. By slowing down the rate of epidermal turnover, the skin thickening will ease and along with other psoriasis treatments, the plaques may clear up altogether.
PUVA is not effective in every case of psoriasis and careful screening will decide if an individual case of psoriasis will benefit from PUVA treatment. There are a host of side effects with PUVA treatment, some of which are severe, like skin cancer. However, in the hands of a skilled dermatologist and with proper clinical evaluation and pre-treatment screening, PUVA treatment can be conducted safely with minimal side effects or risk of complications.