Natural sunlight can have a positive effect and it can even be regarded as a natural treatment for psoriasis. 80% of patients who have been exposed to sunlight improve their psoriasis symptoms. This fact led to the development of therapies for psoriasis with the use of ultraviolet radiation. But before we learn thoroughly about the methods used for light treatment of psoriasis, let’s first talk about what is Psoriasis and try to understand the causes behind it.
What is Psoriasis?
- Psoriasis is a fairly common skin disease. It is estimated that suffers from it the 1-2% of the general population – more than 120 million people – worldwide.
- While psoriasis occurs most frequently between the ages of 15 and 35 years, there are many cases that involve younger or older people.
- In fact, 10-15% of patients with psoriasis are children under the age of 10 years, and many cases are recorded in people aged over 40 years.
- Psoriasis affects both genders equally and is not a contagious disease. Contrary to what many believe, you can not ‘catch’ psoriasis by touching the skin or the clothes of a patient nor the outbreak is a result of poor personal hygiene.
- Instead, the flare-up is a resultant of a combination of factors and especially the hereditary predisposition to impaired functioning of the immune system and cells of the skin.
What are the Causes of Psoriasis:
The etiology of psoriasis is not fully understood, despite the studies that have been made. Research, however, has confirmed the role of genetic factors in the onset and progression of the disease. A hereditary predisposition is found mainly in younger age groups of patients, while the occurrence of psoriasis is more frequent among monozygotic twins.
The appearance of psoriasis in combination with other conditions such as Reiter’s syndrome and Palmoplantar Pustulosis reinforces the belief that it is related to immunological factors. At the same time, it has been associated with pemphigus, the pemphigoid, vitiligo and other autoimmune diseases cause.
An important explanatory role in the appearance of psoriasis plays environmental factors. Environmental factors that often promote the development of psoriasis are streptococcal infections, medications such as lithium, antimalarials, and beta-blockers, and physical and psychological stress. Excessive alcohol use and smoking are also associated with worsening of the disease and making the treatment more difficult. It is interesting to note the fact that a small injury of the skin (sunburn, scratching) can trigger the outbreak of psoriatic lesions (Koebner’s phenomenon).
The most common form of Psoriasis:
Psoriasis usually occurs in the skin but it can also affect joints and in such cases, it is referred to as psoriatic arthritis.
The most common form of skin psoriasis is plaque psoriasis. It is estimated that 8 out of 10 patients suffer from this form of psoriasis.
Plaque psoriasis is characterized by the creation of red plaques on the skin that are covered by silver scales.
This form of psoriasis can occur anywhere on the skin, but the areas of the body that most commonly develop its characteristic red plaques are the elbows, knees, scalp, and torso.
How do you treat psoriasis?
There is no permanent cure for psoriasis, but there are effective sedative treatments aimed to eliminate its damages or at least to reduce them in size and severity. The medication may be strictly topical, systemic, or a combination of them. Choosing the appropriate medication should be made depending on the area, severity, duration of disease, previous treatments, the patient’s age, and whether or not arthritis exists.
In general, treatments for psoriasis are divided into four main categories:
- Topical treatments (treatments applied externally and topical on the site of the lesion)
- Phototherapy (Ultraviolet radiation treatments)
- Oral systemic treatments (drugs taken orally in the form of tablets, or injections to treat the body as a whole)
- Biological therapies (drugs that consist of proteins of human or animal origin which act on the immune system to alter the way diseases are created. These drugs are administered by injections or infusions).
Light Therapy and Psoriasis:
The beneficial effect of sunlight on psoriasis and other dermatoses are well known since antiquity.
Light therapy devices (phototherapy) are recommended when the disease occupies 20-30% of the body surface.
It can also combine with topical or systemic therapy.
Light Therapy – Phototherapy is divide into:
- Phototherapy with UVB (ultraviolet) radiation.
- Photochemotherapy (PUVA), ie exposure of the patient to UVA radiation after per os administration or topical application of psoralen.
Phototherapy with UVB radiation:
UVB radiation is part of the electromagnetic spectrum with wavelengths of 290-320 nm. First introduced by W. Goeckerman in 1925 and it was combined with coal tar. Since then, the therapeutic schemes have undergone several modifications.
Today, irradiation with artificial sources emitting narrowband of wavelength around 311nm (Narrowband UV-B), is gaining ground, because it brings the best therapeutic effect. Due to the low penetration in the skin, it is preferred to use on thin psoriatic plaques, while PUVA acts more effectively on the thicker plaques. The patient has to undergo 3 to 5 sessions weekly.
The initial dose is 70% of the minimal erythema dose (MED) with a progressive increase of the dose. To achieve the optimal therapeutic effects, 15-25 sessions are required.
During photochemotherapy, the patient is exposed to UVA radiation (320-400 nm), 1-3 hours after ingestion or topical application of herbal photosensitizing substances called psoralens.
The exact time depends on the used factor. Usually, is administered 8-MOP (Methoxypsoralen) to the patient. The initial dose of radiation depends on skin type or the minimal phototoxic dose. In 90% of patients, clearance or maximum clinical improvement is achieved after 20-30 sessions (2-3 weekly). The duration of the psoriasis remission is long, longer than that resulting after UVB radiation.
Before the start of phototherapy, a thorough clinical and laboratory testing is necessary to be done, to exclude those who do not meet certain criteria for treatment, as patients with lupus erythematosus or cataracts (PUVA), patients who are taking photosensitizing medications for treating another condition or patients with skin cancer or photoaging.
During the sessions, protective measures must be taken such as covering the face and genitals, wearing sunglasses, and avoiding sun exposure. The safety measures are more stringent after being treated with UVA radiation. Pregnancy and lactation are the absolute contraindications for PUVA. Nausea by administration of 8-MOP is treated by dividing the dose, with food intake, or antiemetics. Phototherapy is combined with topical and systemic factors both for the significant reduction of dose and to minimize the side effects.
PUVA therapy is blamed for skin cancer and causing photoaging. Patients who have undergone more than 150 sessions, should be examined by a doctor at regular intervals.