Phyiological Effects of Ultra-Voilet Radiation

 

 

PHYSIOLOGICAL EFFECTS OF ULTRA-VIOLET

The skin absorbs the majority of ultraviolet light and blocks it from penetrating down to sensitive cells, it functions as a protective barrier. Ultraviolet radiation can harm cells and intracellular structures if they are absorbed by the skin because of the energy they produce. The amount of ultraviolet light absorbed and its wavelength determine how much damage is done and the ensuing response. While UVA can reach the dermal capillary loops, UVC and UVB are absorbed in the epidermis.

Cancer

Long-term exposure to UVB or UVC rays increases the risk of carcinogenesis because these rays can affect DNA and consequently cell replication. It is recommended that patients avoid prolonged exposure to shorter wavelengths of UV radiation on their skin, and treatment regimens should not last longer than four weeks, as there is strong evidence to support the theory that UV radiation causes skin cancer. There is still reason to suspect UVA, even with longer wavelengths, for causing cancer. Patients using sun beds or PUVAs may therefore still be at danger. Determining the Hersey amount (measured in Joules/cm²) is crucial to generating meaningful data regarding acceptable dosage.

Erythema

Histamine-like compounds are released from the superficial dermis and epidermis when cells are damaged. This substance diffuses gradually until enough of it has collected to cause the skin's blood vessels to expand. This explains why the erythema are late. The faster and more intense the interaction, the more histamine-like chemical is created.
The erythrina reaction has been used to categorize ultraviolet dosages administered to patients. Erythema comes in four different degrees. Nowadays, a half-El sub erythemal dose is frequently administered in practice. Wavelengths less than 315 nm cause erythema.

Pigmentation

Within two days after radiation exposure, pigmentation appears. Melanin is produced by skin melanocytes when exposed to ultraviolet light, and it is then transferred to many nearby cells. To shield the cell nucleus from ultraviolet radiation, melanin creates a "umbrella" around it; pigmentation significantly lowers UVB ray penetration.

Thickening of the epidermis

The stratum corneum, the outermost layer, thickens noticeably when the basal layer of the epidermis suddenly becomes overactive. This thickening can reach up to three times its normal thickness. Because of this significant reduction in UV penetration, the dose needs to be raised for successive treatments to have the same effect (as long as peeling hasn't happened). For instance, a 25% increase in El, a 50% rise in E2, and a 75% increase in E3 dosages are required. Given that an E4 dose is often administered to open wounds or ulcers, when an increase in dosage is not necessary, it is doubtful that an E4 dose would be administered to a skin-covered area.

Peeling

When squamation, or peeling, occurs, the epidermis's enhanced thickness finally disappears, significantly reducing the skin's resistance to UV light.

Production of vitamin D

UV light causes 7-dehydrocholesterol in sebum to be converted to vitamin D in the skin. Since vitamin D is required for the absorption of calcium, it plays a part in the normal development of teeth and bones. According to certain theories, administering ultraviolet light to hospitalized patients' bones may help them produce more vitamin D, lessen osteoporosis, and experience fewer fractures overall. This patient group is more vulnerable to the harmful effects of ultraviolet light, such as cancer and cataracts, but the advantages could outweigh the risks with appropriate dosage monitoring.

Solar elastosis and ageing

Continuous exposure to UV light accelerates the skin's natural aging process. The epidermis thins, melanocytes disappear, sebaceous and sweat gland function is compromised, causing dryness, and wrinkles arise from a lack of dermal connective tissue. Fair-skinned people who reside in countries with high levels of sunshine, like Australia or South Africa, are more likely to experience these effects. Severe cases of this include wrinkles on the faces of farmers and sailors. Sunbathers need to understand that extended exposure to ultraviolet light has cumulative, progressive, and harmful effects.

Antibiotic effect

Short UV radiation has the ability to kill bacteria and other microscopic organisms, including fungi that are frequently present in wounds. Research has demonstrated that an E4 dosage efficiently eliminates all of these species.

PHOTOSENSITIZATION

The skin can occasionally react more strongly to ultraviolet light, absorbing it and transferring the energy to nearby skin through a photochemical process. Photosensitizers can be used topically or consumed. It is possible to purposefully cause photosensitivity in a patient by ingesting drugs like psoralen or applying coal tar locally to their skin. On the other hand, a lot of medications and foods can make someone more sensitive to UVR. In real terms, this means that while beginning or ending a medication regimen, patients need to let the physiotherapist know.

ULTRA-VIOLET IRRADIATION INDICATIONS

UV light is used to skin lesions that are infectious or not in order to treat skin disorders.

Unknown

Pustules, papules, and comedones obstructing the hair follicles and sebaceous glands on the face, back, and chest are symptoms of acne. One may provide an E2 dose of ultraviolet radiation with the following objectives:

1. An erythema will increase blood flow to the skin, thereby improving its state.
2. Desquamation will eliminate comedones and permit unrestricted sebum flow, hence lowering the quantity of lesions.
3. The skin will become sterilized by the UVR.

Challenges of Ultraviolet Radiation for Acne

Although ultraviolet radiation has been used to treat acne for a while, there have been some concerns raised over its adverse effects. The required intensity of dose (E2+) frequently causes pain and unsightliness to the patient. Only palliative care is provided, and after UVR, the illness typically returns in a few weeks. Unfortunately, because all of the skin lesions peak at the same time, rather than the normal course of acne, where some resolve while others grow, it may even appear worse a few weeks following UVR. The frequency of treatment may be limited by irregular rates of desquamation, which may also result in a mottled erythema.

Psoriasis

Psoriasis is a skin disorder characterized by localized plaques caused by an excessively fast rate of cell turnover from the surface to the basal layer. The goal of ultraviolet irradiation is to slow down the skin cells' rate of DNA synthesis and, as a result, slow down their multiplication. PUVA or the Leeds regimen can be used for treatment.

Leeds regimen

In the Leeds region, the local application of coal tar mixed into a bath before therapy increases the sensitivity of the patient's skin to UV radiation. Following treatment, the lesions are covered with dithranol cream. When the patient is sensitized, their response to UVR is assessed. The patient receives a sub-erythemal dose (half El) via an air-cooled lamp at 100 cm or a Theraktin tuanel. Every day, the duse is repeated, with each iteration increasing by 12½ per cent. Sub-erythernal doses help psoriasis, however real sunburn or high E1 + dosages make it worse.

PUVA

A sensitizing medication made from psoralen is taken by patients following a photodynamic therapy two hours before UVA exposure. When UVA is present, psoralens binds to DNA in the cell nucleus, preventing DNA synthesis and cell division.

Skin Typing for PUVA Dosage Adjustment

As the dosage for a PUVA regimen is measured in J cm (joules per square centimeter), specialized equipment must be used on a regular basis to assess the generator's output. The patient's skin type determines the dosage, which is gradually increased in terms of applied energy density rather than duration. The skin types listed below are characterized in order of least to most reactiveness:

• 1.     constantly burn and never tan;
• 2   always buru, slightly tan;
• 3.     occasionally burn and always tan;
• 4.     never burn and always tan;

skin with a moderate pigmentation, such as Mediterranean or Mongoloid; VI skin with a heavy pigmentation, such as black.
Patients with skin type I, for instance, get a minimal dose that, within 72 hours of irradiation, causes only mild erythema. This dose is increased by 0.5 J cm-² for each treatment. Because of the sensitizing psoralen medication, these patients need to shield their eyes from sunlight during the day and wear dark glasses. But there are hazards associated with this medication.

Skin wounds

Infected wounds

Pressure sores, surgical incisions, ulcers, and other infected skin lesions can all be treated with ultraviolet light. The ultra-violet light's objectives are to eliminate bacteria, eliminate slough (infected dead material), and encourage healing. UVB is typically administered locally to the lesion with an E3 or E4 dose using a Kromayer lamp to accomplish this. Since there is no skin covering the wound, a progressive dose increase is not required.

Non-infected wounds

The goal of UVR therapy is to accelerate repair by inducing granulation tissue formation after infection has resolved or if it never existed in the first place. While longer UVA photons promote granulation tissue growth, shorter UVB rays harm it. As a result, a filter of some kind is employed to permit the emission of UVA but not UVB. Cellophane or Blue Uviol glass could be used for this filter.

Complete skin

If intact skin is located in a pressure point where it is prone to breaking down, UV treatment may be applied. To enhance skin conditions and boost circulation through the area, an El dosage is administered. This can also be applied to more resilient ailments like chilblains.

Counter-irritation

In the past, ultra-violet was applied to the area where a deep-seated discomfort (such as the lumbar spine) was present in order to strongly counterirritate it. After administering an E3 or E4 dose, a dry dressing was applied to the affected area. The deeper pain should theoretically be concealed by the erythema's surface-level discomfort, which is supported by contemporary pain modulation ideas as a way to create endogenous opiates from PAG, etc. (see p. 100). Ultraviolet therapy has already mostly been replaced by other forms of treatment, while some long-term benefit was believed to be possible as long as additional treatments, including exercise, were started during this time of respite.