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Ultraviolet Therapy
Ultraviolet Radiation
• In electromagnetic spectrum UVR ranges
from 2000 to 4000 Å
• Divided into three ranges:
– UV-A- near UV- 3200 to 4000 Å
• Little or no physiologic effect
– UV-B- middle UV- 2900 to 3200 Å
• Associated with sunburn and age-related skin
– UV-C- far UV- 2000 to 2900 Å
• Bactericidal
Ultraviolet Radiation
• UVR apparatus most likely to be used
would generate UVR in UV-B, UV-C or
both ranges
• UVR is absorbed within first 1 to 2 mm
of human skin
• Most of physiologic effects are
• Used to treat various skin disorders
Effect On Cells
• Exposure of skin to UVR causes chemical
excitation of cells which leads to
physiologic changes within these cells
• Alteration of cell biochemistry and
cellular metabolism which affects
synthesis of DNA and RNA
• This leads to alterations in protein and
enzyme production
Short-Term Effects on Skin
• Skin consists of two
– Epidermis
• Contains keratinocytes
which produce keratin,fibrous protective protein
of skin
– Dermis
• Papillary layer - rich blood
• Reticular layer - heavy
connective tissue
containing fibroblasts,
histocytes, and mast cells
• Generalized response to UVR exposure
culminates in development of an acute
inflammatory reaction
• End results of active inflammation are
– Erythema - reddening of skin associated
with sunburn
– Pigmentation -tanning
– Increased epidermal thickness
• Inflammatory response characterized by
local vasodilation and increased
capillary permeability causing erythema
• Permits certain proteins to move from
capillaries into dermis resulting in a
change in osmotic pressure
• Water drawn into area and edema
• Phagocytic cells eliminate dead cells
• Over sensitization to UVR as a result of
excitation of a chemical by UVR
• Acute effects of UVR exposure can be
exacerbated if certain chemicals or
medications are present on skin or in
• Increase of pigmentation in skin
• Protective mechanism activated by UVR
• Increase of melanin (pigment
responsible for darkening) within skin
causes tan
– Functions as a biologic filter of UVR
• By scattering radiation
• By absorbing UVR
• By dissipating absorbed energy as heat
• Immediate tanning occurs following
UVR exposure
– Appears most often in darkly pigmented
– Represents the darkening of melanosomes
already present in the skin
– Begins to fade 1 hour after exposure and is
hardly noticeable 3 to 8 hours
• Delayed tanning results from formation of
new pigment (melanin) through
– Delayed tanning usually becomes apparent
72 hours after UVR exposure
Artificial Tanning Devices
• Manufacturers claim tanning beds
produce only UVR in UV-A spectrum
and are safe
– Production of this type of UV-A generator is
largely unregulated
– Effects of long-term exposure to UV-A are
– Caution should be exercised before using
an artificial source to expose to UVR
Long-Term Effects on Skin
• Premature aging of the skin
– Dryness, cracking, and a decrease in
elasticity of skin resulting from epidermal
solar elastosis
• Alteration in the skin's elastic fibers
• Linked to UVR-induced DNA damage
Long-Term Effects on Skin
• Skin cancer
– Most common malignant tumor found in
– Damage to DNA suspected as cause
– Major types of skin cancer
• Basal cell carcinoma( rarely metastasizes)
• Squamous cell carcinoma (metastasizes in 5%)
• Malignant melanoma (Usually metastasizes
– Rate of cure exceeds 95% with early
• Sunscreen’s effectiveness in absorbing
sunburn inducing radiation is expressed
as sun protection factor (SPF)
• SPF of 6 indicates you can be exposed
to UVR six times longer than without a
sunscreen before receiving a minimal
erythemal dose
Effect On Eyes
• UVR exposure of the eyes causes an
acute inflammation called photokeratitis
– Delayed reaction occurring within 6 to 24
– Conjunctivitis develops, accompanied by
erythema of adjacent facial skin
– Sensation of a foreign body on eye
– Photophobia
– Increased tear production
– Spasm of the ocular muscles
Systemic Effects
• Photosynthesis of vitamin D following
irradiation of skin by UVR in UV-B range
– UVR can be used as treatment for
disorders of calcium and phosphorus
metabolism, such as rickets and tetany
– Treatment of choice for such problems is
dietary supplementation
Ultraviolet Generators
Carbon arc lamp
Xenon compact arc lamp
Fluorescent ultraviolet lamp (blacklight)
Mercury arc lamp
Carbon Arc Lamp
• Composed of two carbon electrodes
• Two electrodes move slightly apart
causing current to arc across small gap
• UVR is emitted between 3500 and 4000
• Electrodes gradually burn and must be
– Burning is noisy and causes an unpleasant
Xenon Compact Arc Lamp
• Composed of compressed xenon gas
enclosed in a vessel
• Electric arc passed through gas
• Gas is heated to 6000° C
• Emits infrared, visible, and UVR in
range of 3200 to 4000 Å
Fluorescent UV Lamp
• Low-pressure mercury lamp
• Tube of UV-transmitting glass coated
with phosphors
• Phosphors are fluorescing substances
that absorb the UVR and then reemit it
at a longer wavelength
• UVR emitted ranges from 3000 to 4000
Mercury Arc Lamp
• Most likely kind of UVR lamp to be used
• Either low-pressure or high-pressure
mercury arcs
– Mercury contained in a quartz envelope
– An electric arc passes through vaporizing
– At 8000° C atoms become incandescent
and emit ultraviolet, infrared, and visible
Mercury Arc Lamp
• High-pressure = Hot Quartz
• Most of UVR produced falls within UV-B
• Mainly used to produce erythema and
accompanying photochemical reactions
Mercury Arc Lamp
• Low-pressure = Cold quartz lamp
– Temperature of the quartz envelope is about 60°
– UVR spectrum limited to 1849 Å and 2537 Å
– Does not require a warm up or cool down period,
and is used mainly where bactericidal effect of
UVR is desired
Techniques of Application
• Effectiveness of lamp assessed by
determining skin sensitivity to UVR
– Measured by the minimal erythemal dose
• Exposure time needed to produce a faint
erythema of the skin 24 hours after exposure
• Question patient regarding photosensitizing
– Area of skin to be tested should have
Measuring MED
• Patient is draped except for test site
• Piece of paper with five cutouts 1” square and
1”apart placed over the test site
• Height of lamp from patient adjusted to same
level as for treatment
• Shutters are opened and cutouts exposed at
15-sec intervals 15, 30 , 45, 60, and 75 secs.
Determining MED
Patient returns in 24 hours and a visual
inspection determines MED
• Areas tested that reveal no erythema 24 hours
after testing have received a suberythemal
• Areas showing erythema at 24 hours have
received a minimal erythemal dose.
• Erythema still present at 48 hours = 1st degree
erythemal dose
• Erythema persists from 48-72 hours = 2nd
degree erythemal dose
• Erythema lasts past 72 hours= 3rd degree
erythemal dose
Determining MED
• 1st-degree and 2nd-degree doses can
be estimated
– 1st-degree erythemal doses approximately
correspond to 2.5 times minimal erythemal
– 2nd-degree doses correspond to 5 times
minimal erythemal dose
Determining MED
• Since human skin adapts to UVR
exposure, MED will gradually increase
with repeated treatments
• Necessary to gradually increase
exposure time to achieve the same
• Once determined it is increased 5
seconds per treatment
• Height of lamp remains constant
Positioning The Lamp
• Apply cosine law and inverse square law
• Distance of lamp must be kept constant
if intensity of treatments is to be equal
• Generally standardized at each clinic
usually ranging from 24 to 40 inches
Treatment Technique
• Patient should be draped and wear eye
• Consistency in positioning of lamp is
– Must be the same as in MED test
• Clinician must also wear goggles
• Open lamp shutters and begin timing
Clinical Applications
• Most common use of UVR is in
treatment of dermatologic conditions
such as psoriasis and acne and hard to
cure infectious skin conditions such as
pressure sores
• Development of oral and topical
medications has greatly reduced the
use of ultraviolet
Indications for Ultraviolet Therapy
Aseptic wounds
Pityriasis rosea
Tinea capitum
Septic wounds
• Pressure sores
• Osteomalacia
• Diagnosis of skin
• Increased vitamin D
• Sterilization
• Tanning
• Hyperplasia
Contraindications for Ultraviolet
• Porphyrias
• Pellagra
• Lupus
• Sarcoidosis
• Xeroderma
• Acute psoriasis
• Acute eczema
• Herpes simplex
• Renal and hepatic
• Diabetes
• Hyperthyroidism
• Generalized dermatitis
• Advanced
• Active and progressive
pulmonary tuberculosis