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Sunburn
 What
is sunburn?
Sunburn is simply a burn or erythema (reddening) and
oedema (swelling) on your skin from excessive exposure
to the sun's rays, more specifically the ultraviolet
(UV) radiation that is emitted from the sun. Sunburn
may also occur from exposure to other UV light sources
such as solaria or tanning salons.
At a cellular level, sunburn is associated with microscopic
changes in the skin. There is the formation of UV induced
sunburn cells and a reduction in Langerhan cells and
mast cells, which play an essential part of the body's
immune defence system.
What causes sunburn?
To better understand the causes of sunburn we need to
take a look at some basic principles of the electromagnetic
(light) spectrum. This spectrum is divided according
to wavelength into ultraviolet (<400nm), visible
(400-760nm), and infrared (>760nm). The ultraviolet
(UV) spectrum is further divided into 3 broad areas:
· Ultraviolet A (UV-A) = 320-400nm
· Ultraviolet B (UV-B) = 290-320nm
· Ultraviolet C (UV-C) = <290nm
UV-C radiation is filtered out or absorbed in the outer
atmosphere so does not pose a problem to humans. It
is UV-A and UV-B radiation that are the primary causes
of sunburn. Although both wavelengths are implicated
in sunburn, the skin reacts differently to each one.
Reactions to UV-A and UV-B radiation
| UV-A |
UV-B |
| Less potent than UV-B but is the wavelength that
reaches the surface of the earth most (about 90%
at midday) Also penetrates into the middle skin
layer (dermis) and subcutaneous fat causing damage
to the site where new skin cells are created Long-term
exposure causes injury to the dermis resulting in
ageing skin |
Much more potent at causing erythema
About 90% is absorbed by the surface skin layer
(epidermis) Epidermis responds by releasing chemicals
that cause the reddening and swelling characteristic
of the early signs of sunburn Repeated exposure
causes injury to the epidermis resulting in ageing
skin |
Who is at risk of sunburn?
Skin phototyping categorises people into one of six
groups based on baseline skin colour and the tendency
to tan and/or burn when exposed to UV radiation.
| Skin Phototype |
Typical Features |
Tanning ability |
MED (mJ/cm2) |
| 1 |
Pale white skin, blue/hazel eyes, blond/red hair
|
Always burns, does not tan |
15-30 |
| 2 |
Fair skin, blue eyes |
Burns easily, tans poorly |
25-40 |
| 3 |
Darker white skin |
Tans after initial burn |
30-50 |
| 4 |
Light brown skin |
Burns minimally, tans easily |
40-60 |
| 5 |
Brown skin |
Rarely burns, tans darkly easily |
60-90 |
| 6 |
Dark brown or black skin |
Never burns, always tans darkly |
90-150 |
People with type I skin phototyping are at much greater
risk of sunburn than their type VI counterparts. The
amount of UV radiation, measured in energy per unit
area, to produce erythema at an exposed site is called
the minimal erythema dose (MED) and this is significantly
lower in people with a low skin phototype grading.
Other factors that increase the incidence of sunburn
include:
· Regions situated closer to the equator
· Areas at high altitude - UV radiation increases
4% for every 300m increase in elevation
· Skin exposure between 10am and 2pm - 65% of
UV radiation reaches the earth between these times
· Clear skies: clouds and environmental pollution
reduce UV radiation
· Environmental reflection - UV radiation is
80% reflected by snow and ice
What are the signs and symptoms of sunburn?
The signs and symptoms of sunburn differ for each individual
according to their skin phototype and length of exposure
to UV radiation. Fifteen minutes of midday sun exposure
may cause sunburn in a white skin person, while a darker
skinned person may tolerate the exposure for hours.
Signs and symptoms usually occur after 2-6 hours of
exposure and peak at 12-24 hours, they may include:
· Erythema (redness)
· Oedema (swelling)
· Tenderness and/or irritation
· Skin feels hot to touch
· Pain
· Blistering (severe cases)
· Chills and fever (severe cases)
Around 4-7 days after exposure skin may start to peel
and flake off.
In severe cases of sunburn, severe skin burning may
result in second-degree burns, dehydration, electrolyte
imbalances, secondary infection, shock or even death.
What is the treatment?
The treatment of sunburn is to provide relief of the
discomfort it can cause. This can be achieved with the
use of analgesics (pain-killers), cool baths, aloe vera
lotions and moisturisers.
However, sunburn is better prevented than treated. Sun
protection is your best defence against sunburn and
other damaging effects of UV radiation.
· Avoid sun exposure, especially between 10am
to 2pm
· Wear protective clothing, including wide-brimmed
hats
· Regularly apply sunscreen with a Sun Protection
Factor (SPF) of 30+
An oral food supplement containing Polypodium leucotomas
may provide additional oral photoprotection and reduce
sunburn.
If you are inadvertently exposed and expect to be sunburned:,
you may lessen the severity of the burn with the following
measures:
· Take two aspirin immediately and then two
every four hours
· Apply a topical steroid to exposed areas twice
daily for two or three days
What are the long-term consequences?
It is now clearly apparent that the long-term consequences
of overexposure to the sun or other sources of UV radiation
are significant (click on links below for further information).
One blistering sunburn is said to double the likelihood
of developing skin cancer.
· Premature aging skin and wrinkling
· Brown spots and freckles (lentigos)
· Development of pre-malignant lesions (solar
keratoses)
· Development of skin cancer (e.g. melanoma,
basal cell carcinoma, squamous cell carcinoma)
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