Phototherapy in Dermatology: What is Important to Know

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Natalia Sachuk, head of the clinic of restorative medicine "Farmosa", dermatocosmetologist, trichologist, member of the All-Ukrainian Association of Trichologists, the Association of Preventive and Anti-Aging Medicine, the Ukrainian Academy of Dermatovenereology (Ukraine, Vinnytsia)

Marina Erokhina, chief physician of the restorative medicine clinic "Farmosa", dermatologist, trichologist, member of the Ukrainian Academy of Dermatovenereology, Ukrainian Society of Aesthetic Medicine, All-Ukrainian Association of Psoriasis (Ukraine, Vinnytsia)

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The spectrum of sunlight is the source of life for all living things, including humans. The radiant energy of the sun, in addition to the thermal effect and the importance for vision, has a beneficial therapeutic effect on the entire body. In addition, UV radiation is successfully used in dermatology to treat a number of diseases.

The Sun: Benefits and Dangers

Acting through the visual analyzer, light energy affects the overall tone of the body, mood, sleep rhythm, etc. During irradiation of the skin, photochemical reactions occur in the body, which have a serious effect on metabolism. Ultraviolet rays with a wavelength of 290 to 315 nm have the strongest biological property. Under the influence of ultraviolet rays, vitamin D is formed in the skin. Direct sunlight kills tuberculosis bacteria in a few minutes, staphylococci - in 15 minutes, typhoid bacilli - in an hour. But with a lack of light, numerous disturbances in the vital activity of the body occur: children develop rickets, caries, bone strength decreases, functional disorders of the nervous system appear.

If the sun exposure is too long, the nervous system may become fatigued, reflex disorders may occur, and heat stroke may occur. A separate topic is the negative impact of ultraviolet radiation on human skin – the so-called photodamage of the skin. Chronic exposure results in the appearance of various nevi on the skin, melanomas, hyperpigmentation and dyschromia, photoaging of the skin, the occurrence of photodermatoses and phototoxic reactions. Ultraviolet radiation often provokes blistering reactions on the irradiated skin, the mechanism of which is associated with the presence of circulating antibodies. The formation of urticaria (skin rashes) as a phototoxic reaction can be caused by any medications – tetracyclines, oral contraceptives, amiodarone, quinidine, fluoroquinolones, griseofulvin, sulfonamides, etc. Factors such as pregnancy and childbirth can change or enhance the reaction to ultraviolet radiation. And the combined effect of the sun and other irritating external factors – for example, chlorine in the pool, working with chemically active substances, the use of low-quality, “aggressive” cosmetics, various creams, deodorants, oils – can cause a phototoxic reaction.

Solar urticaria can be caused by light of different wavelengths, even UVA in a solarium. The clinical manifestations of solar urticaria are peculiar: immediately after irradiation, rashes appear on exposed areas of the skin, the nature of which depends on the exposure time. With short-term insolation, rashes of small pink-red itchy urticarial elements on unchanged skin, which soon turns red, are most common. After prolonged insolation, rashes of larger pale pink blisters with a more intensely colored border along the periphery are mainly observed. Urticaria, as a rule, disappear within 15-30 minutes, erythema - after 2-3 hours. The histopathology of solar urticaria is characterized by edema in the upper part of the dermis, expansion of the papillae, flattening of the epidermal processes. Moderate spongiosis and intracellular edema occur in the epidermis.

Light therapy

However, some dermatological diseases show a tendency to improve when exposed to ultraviolet radiation, which is actively used in the arsenal of treatment standards in modern European dermatology. These are diseases such as psoriasis, atopic dermatitis, neurodermatitis, lichen planus, vitiligo, etc. Even some patients with photodermatoses can achieve a 10-20-fold increase in resistance to sunlight when using phototherapy. UV irradiation is also used for preventive purposes - to compensate for natural UV deficiency, hardening, healing, increasing resistance to infectious and pustular skin diseases, as well as for the treatment of pyoderma, erysipeloid, neurodermatitis, pruritus, acne, alopecia areata, vitiligo, etc.

UVA and UVB rays of the ultraviolet radiation spectrum are used in treatment. The ability of a particular type of radiation to penetrate human skin depends on the wavelength. This is very important when prescribing treatment for skin diseases, depending on where the pathological process is localized, in which layers of the skin. For example, medium-wave rays (UVB) penetrate the stratum corneum, reach the spinous layer of the epidermis and have an anti-inflammatory, immunomodulatory effect, mainly immunosuppressive, affecting epidermal keratinocytes and Langerhans cells. And long-wave rays (UVA) reach the papillary and reticular layers of the dermis. Infrared rays, passing through the epidermis and dermis, reach the subcutaneous fat. Penetrating into deeper layers of the skin, they affect dermal fibroblasts, dendritic cells, endothelial cells and inflammatory infiltrate cells (T-lymphocytes, mast cells, granulocytes). At the cellular level, ultraviolet rays affect the production of inflammation mediators (cytokines) that have anti-inflammatory and immunosuppressive effects, inducing apoptosis of cells involved in the pathogenesis of the disease.

Phototherapy rules

>The effectiveness of phototherapy and the safety of its use depends on the following factors:

• skin sensitivity and reaction to ultraviolet radiation;
• the intensity of ultraviolet lamp radiation;
• the correct selection of medications used during phototherapy.

Before starting phototherapy, it is recommended to determine the individual sensitivity of the patient to light by determining the minimum erythemal dose (DER). The DER is determined for the type of lamp selected for therapy by performing test irradiations on the part of the skin that is not usually exposed to sunlight (e.g., the buttock). The DER is defined as the lowest dose of irradiation at which erythema becomes visible. Erythema is determined 24 hours after irradiation. The DER is the dose of ultraviolet radiation in J/cm2 that caused redness (erythema) after 12-24 hours on one of the irradiated areas of the skin. The first therapeutic dose of UVB radiation is 70% of the DER established during testing.

A number of phototherapy devices have built-in devices that record the radiation intensity and automatically calculate the radiation dose.

To account for the procedures administered, a unit was introduced - the radiation dose, designated in J/cm2. It depends on the radiation intensity and the time of irradiation.

There are four types of phototherapy for skin diseases:

• selective phototherapy (SPT) - a combination of medium-wave radiation at a wavelength of 295-330 nm with long-wave ultraviolet irradiation (UVA);
• narrow-wave UVB phototherapy with an emission maximum at a wavelength of 311 nm;
• photochemotherapy (PUVA) - a combined use of long-wave ultraviolet irradiation (UVA) with photosensitizers;
• phototherapy using long-wave ultraviolet irradiation of a narrow spectrum (UVA-1) at a wavelength of 370 nm.

Narrowband radiation therapy

Recently, there has been a tendency to use narrow-band radiation spectrums in the treatment of skin diseases, which have a selective effect on skin structures, with less pronounced side effects. The superiority of narrow-band therapy is noticeable in the treatment of psoriasis, atopic eczema, in the prevention of polymorphic photodermatosis and the correction of vitiligo.

In vitiligo, for example, this spectrum of radiation interrupts the progression of skin depigmentation and promotes pigment restoration in vitiligo lesions by stimulating the proliferation of so-called residual melanocytes in the epidermis and hair follicles. In psoriasis, both epidermal keratinocytes and skin lymphocytes can be targets for UV rays. Immunosuppression, changes in cytokine expression and the cell cycle - all these factors may play an important role in explaining the therapeutic effect of ultraviolet radiation.

Selective phototherapy is carried out using devices that use lamps that emit ultraviolet radiation of the mid-wave range UVB 285-350 nm, especially relevant are UVB 311 nm lamps.

Selective phototherapy is performed using two methods – with or without determining the minimum erythemal dose (MED). Therapy without determining the MED usually begins with a UVB dose of 0.05–0.1 J/cm2. During the next procedure, if there is no erythema, the dose is increased by 0.05–1.0 J/cm2. The course of treatment includes 20–30 procedures.

Peculiarities of psoriasis treatment

There is a method of irradiating with UVB 311 nm 3-4 times a week, with a gradual increase in the radiation dose. In case of regression of rashes, it is necessary to constantly increase the dose of UVB rays. If, for example, on the 2nd week with a dose of UVB radiation of 0.5 J/cm2, the disappearance of clinical manifestations on the skin is observed, the dose of UVB radiation of 0.5 J/cm2 can remain unchanged in the following days of treatment. The absence of regression requires an increase in the dose. The course is 20-30 procedures.

Features of the treatment of parapsoriasis

Medium-wave ultraviolet radiation of a narrow spectrum of 311 nm is used to treat plaque and droplet forms of parapsoriasis. The irradiation regimen is from 3 to 4 times a week. During treatment, a patient with plaque parapsoriasis may develop new, previously unseen rashes on the skin of the trunk and limbs. Their appearance does not require cancellation of the prescribed course. Treatment is carried out until the clinical manifestations on the skin completely disappear.

Features of treatment of lichen planus

Irradiation is performed three times a week. It is recommended to use erythemal doses of UVB radiation throughout the entire period of therapy. The timing of the end of treatment is determined by the clinical effect - until complete regression of the rash.

Features of the treatment of atopic dermatitis and pruritus

Since these two diseases have a common nature, the approach to treatment with medium-wave ultraviolet radiation of 311 nm is the same: the irradiation regimen can be from 3 to 4 times a week. Treatment begins with a minimum (suberythemal) dose of UVB rays and continues until the clinical manifestations on the skin completely disappear. The course of treatment can be from 20 to 30 procedures.

Features of the treatment of vitiligo

Treatment of vitiligo with medium-wave ultraviolet UVB 311 nm is based on the same principles that were developed for the treatment of vitiligo with ultraviolet radiation, i.e. it is carried out at erythemal doses, when erythema occurs on depigmented areas and foci of pigmentation appear. It is recommended to carry out no more than 20 procedures per course of treatment. To achieve a positive effect of therapy, it is necessary to carry out several courses, with a break of 20-30 days.

Features of baldness treatment

Treatment of both total and focal forms of baldness is carried out on erythema doses, that is, when erythema appears on the skin. The mode is irradiated – 2– 3 procedures per week, course – no more than 10–15 procedures. To achieve a positive effect of therapy, it is necessary to conduct several courses of treatment, with a break of 20-30 days.

Contraindications and side effects

There are the following contraindications to UVB 311 nm phototherapy: malignant tumors, bleeding tendency, functional kidney failure, increased nervous excitability, increased sensitivity to light, cachexia, thyrotoxicosis, hirsutism, generalized dermatitis, lupus erythematosus, cardiovascular insufficiency II-III degree, a severe form of atherosclerosis, hypertensive disease of the III stage, malaria, tuberculosis of the lungs, kidneys, larynx in an active form.

Therefore, treatment is carried out only after a clinical and laboratory examination of the patient. To rule out contra-indications, consult a therapist, endocrinologist, ophthalmologist, gynecologist; general analysis of blood and urine; blood test for the content of glucose, bilirubin, cholesterol, total protein, final nitrogen, urea, prothrombin, transaminases.

It is desirable to combine treatment with ultraviolet radiation with the use of drugs of general and local action – retinoids (neotigazone), calcipotriol (daivonex, forcal). This increases the effectiveness of the therapy, increases the period of remission of the disease and reduces the total dose of ultraviolet radiation.

Clinical symptoms of the side effects of ultraviolet rays include the following: the appearance of a yellow skin tone, uneven pigmentation, lentigo, telangiectasia; thickening of the skin (solar keratosis); decrease in turgor and elasticity; dehydration and, as a consequence, – wrinkles All these signs are called one term: "photoaging of the skin". Under the action of ultraviolet radiation, chain reactions of lipid peroxidation are triggered, a large amount of free radicals are formed, which damage cellular structures.

To prevent unwanted side effects of ultraviolet radiation, before carrying out phototherapy procedures, it is necessary to lubricate areas of healthy skin with sunscreens with filters for the UVA spectrum of SPF 60. During treatment and after its completion, the skin should be intensively and purposefully moisturized with hydrating agents that restore the hydrolipidic mantle with emollients. They may include active moisturizing ingredients (shea oil, glycerin, linoleic acid, etc.), substances that accelerate skin regeneration processes (allantoin, aloe extract), anti-inflammatory agents (alpha-bisabolol), as well as antioxidants (vitamins E and C, bioflavonoids). In the recovery period after the end of phototherapy, antioxidant preparations containing alpha-tocopherol, vitamin C, and carotenoids are prescribed internally and externally.

Thus, knowledge of the mechanisms of photobiological action, indicated for the use of this or that variant of phototherapy, methods of prevention of unwanted effects of ultraviolet rays on the skin makes phototherapy one of the effective and safe methods of treatment of skin diseases.

Published for the first time: KOSMETIK international journal, №2/2013