Ultraviolet Radiation By Prof.Dr. Gehan Mosaad

Objectives At the end of this lecture you should be able to: Define UVR Identify how UVR is produced Recognize the physiological effects of UVR Know therapeutic uses of UVR Recognize the contra-indications of UVR

Ultra-Violet Radiations (UVR) are electromagnetic radiations lie between visible light & x-ray wavelengths extended from 400 nm to 100 nm are absorbed within first 1 to 2 mm of human skin most of physiologic effects are superficial don’t produce heat, produce physiological effects by nonthermal mechanisms, its effects are mainly chemical used to treat various skin disorders Divided into three ranges: UVA, UVB, UVC.

The Electromagnetic Spectrum

Classification of UVR Wavelength Type 315 - 400 nm UVA (long) UVB (medium) Below 280 nm UVC (short)

Production of Ultra-Violet Radiations The natural source of UVR is the sun, that emit all types of UV. UVR is produced artificially for therapeutic purpose by the passage of electric current through an ionized vapor , often mercury vapor. UVR are usually produced by mercury vapor lamps as follow: These lamps consists of a Quartz burner tube evacuated of air and containing traces of argon gas and mercury under low pressure (to allow gas to conduct current) An electrode is inserted at each end of the burner tube. The current is applied to the electrodes, the mercury vaporizes and the passage of the electron through the vapor establishes the UVR arc.

Production of Ultra-Violet Radiations

Physiological effect of UVR UVR are absorbed by the skin. It penetrates the skin to a maximum depth of 2 mm, so that all UVR will be absorbed by the cells in the epidermis and the superficial dermis. UV has been shown to cause skin erythema, tanning, epidermal hyperplasia, and vitamin D synthesis. It is thought that these effects are the result of absorption of electromagnetic energy by the cells of exposed tissue, causing chemical excitation and facilitation of photobiological processes Its effects Local effects General effects

Local Effects of UVR 1- Erythema It is the redness of the skin. It is the first observable effect of UVR. If UVR is absorbed by the skin, the energy released is sufficient to cause damage to the cells and intracellular structures This damage depends on the wavelength and the amount of UV absorbed. Damage of cells causes the release of histamine like substance from the epidermis and superficial dermis that accumulated around blood vessels in skin to make dilatation of capillaries.

Erythema The greater the release of histamine likes substance the stronger and sooner the reaction. The shorter the wavelength, the greater the erythema (why). Erythema produced primarily in response to UVB. The erythema reaction has been used to classify doses of the UVR given to the patient. There are four visible degrees of erythema

Description of the degrees of Erythema Dose Latent period Appearance Disappearance Pigmentation Desquamation Relation to E1   E1 6-12 hrs Slightly Pink) < 24hrs Nil 1 E2 4-6 hrs Red 48 hrs slight powdery 2.5 E3 1-4 hrs Fiery-red and painful 72 hrs marked In thin sheets 5 E4 (Destructive dose) < 2 hrs angry red very painful week or more Blister and thick sheets 10

Local effects of UVR (cont.) 2- Pigmentation (tanning): It develops within two days of irradiation UVR stimulates formation of melanin that present in the deep region of the epidermis and upward migration of it into more superficial layers. The melanin forms as umbrella over the nucleus of the cell to protect it from UVR, so pigmentation reduces the penetration of UVR to deeper tissue layers, it is thought that tanning is a protective response of the body.

Local effects of UVR (cont.) 3-Growth of epithelial cells (Epidermal hyperplasia): Epidermal hyperplasia is a thickening of the layer of the skin, occurs approximately 72 hours after exposure to UV radiation as a result of repairing process following erythema. Cells in the basal cell layer of the skin proliferate to replace the cell in the epidermis which are damaged or destroyed by UVR. Thickening of the skin is three time than before UVR

Local effects of UVR (cont.) 4- Desquamation (peeling): It is the casting off of dead cells from the surface of the skin which have been destroyed by UVR. The extent of the desquamation is proportional to the intensity of the erythema With mild degrees of erythema, fine desquamation may be seen after repeated exposure to UV. After its occurrence, the resistance of the skin to UVR is lowered.

Local effects of UVR (cont.) 5- Antibiotic effect (bactericidal effect): Mainly UVB enhance destruction of viruses, bacteria, and other small organisms found on the skin surface.

General Effects 1- Formation (production) of vit D Vit.D is accelerated by UVR as the skin absorbs UVB radiation in the sunlight and coverts provitamin D in skin, such as 7-dehydrocholestrol , to vitamin D3. Vit.D3 in its active form acts on the intestine to facilitates absorption of calcium & phosphorus into the blood stream and act on bone to facilitate calcium exchange and bone formation to prevent rickets.

(General effects (cont. 2- The esophylactic effect The resistance of the body to infection is increased (enhanced), particularly if general irradiation of UVRA is given. This effect is due to stimulation of the Reticulo-endothelial system (the cells which ingest bacteria and produce antibodies against bacteria and toxins).

Reticulo-endothelial system

General effects (cont.) 3- Ageing of the skin (Solar Elastosis) Continued exposure to strong sunlight results in premature aging of skin as a result of: thinning of the epidermis, loss of epidermal ridges loss of melanocytes dryness as result of poor function of sebaceous and sweat glands wrinkling from lack of dermal connective tissue.

General effects (cont.) 4-Immune Suppressive Effects UVR appears to trigger immunosuppressive effects, both locally and systemically UVR destroys Langerhan's cells and stimulate the proliferation of suppressor T cells (lymphocytes) that inhibit antibodies production. Prolonged exposure to UVR may contribute to the development of skin cancer due its immunosuppressive effects.

General effects (cont.) 5- Effects on eyes Acute effects of expose of eyes to UVC and UVB are: inflammation of membrane that cover the inside of eye lids inflammation of cornea that can result in sever pain.

Therapeutic Uses of UVR 1- Acne 2- Psoriasis 3- Incipient pressure areas 4-Wound healing 5- Eczema

Acne 1- Acne is a chronic inflammation of the sebaceous gland with blocking of its duct, especially affecting the face, chest and back. Effects of UVR will produce: Desquamation opens the blocked pores and hair follicles, Erythema improves the condition of the skin, UVR stimulates growth of healthy epidermis, and destroys the infecting organism.

2-Psoriasis Psoriasis is a common benign, acute ,or chronic inflammatory skin disease of unknown cause, characterized by bright red plaques with silvery scales, usually on the knee, elbow, and scalp, associated with mild itching. The therapeutic effect of UV in the treatment of this condition may be inactivation of cell division and decrease the DNA synthesis in the cells of the skin with the resultant decrease in the proliferation of the skin cells. Or: altered leukocyte behavior and immunological activity , as well as effects on cell metabolic function.

Incipient pressure area Incipient pressure areas UVR prevents the skin over an incipient pressure area from breaking down and produce an open, infected wound. UVR improves the skin condition, stimulates the growth of epithelial cells, and destroy surface bacteria.

4-Wound healing UV may be used to promote the healing of non-infected and infected open wounds, such as surgical incisions, pressure areas, or ulcers, through the following: 1- stimulate epithelial cell hyperplasia 2- improve skin condition by increase blood supply 3-prevent infection by destruction of any surface organism. 4- destroy and remove infected material. UVC is the frequency band most commonly chosen.

5- Eczema Eczema is an inflammatory response in the skin with associated edema. The patient suffers marked itching with redness, vesicles and exudation of serum on the skin. UVR helps to control this condition through: Erythema that improve skin condition Antibiotic effect as it sterilize the skin surface.

Photo-chemotherapy is the treatment of skin disease by exposure to UVR combined with photosensitizing agent e.g. PUVA (psoralen plus UVA). The drug is given to the patient 2 hours before irradiation to UVA. The patient will become more sensitive to UVR which will produce an erythema at lower intensities than normal. Many disorders show partial or complete response to PUVA: Psoriasis, Eczema.

Contraindications Dermatological conditions: acute eczema, lupus erythematosis, Hypersensitivity to sunlight (photo-allergy) Febrile disorders Recent deep x-ray therapy Pulmonary tuberculosis or tumors Severe cardiac disturbances  Hyperthyroidism. Erythema , if patient’s skin still present an erythema.

Assignment Comparison between erythema of IRR and UVR

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