| What
is solar urticaria?
Solar urticaria (SU) is an abnormal reaction
to sunlight or artificial light.
When exposed to light, the skin cells of someone
with solar urticaria release potent chemicals (including histamine),
causing their blood vessels to open and fluid to collect within
the skin. Their skin feels itchy and has red patches, which
may be swollen.
These may look like weals or a nettle rash,
and can take up to an hour to appear after exposure to light,
then coming on quickly and settling within a similar period.
There is no permanent change to the skin.
If a large enough area of the body is affected,
the loss of fluid into the skin may result in light-headedness,
pallor and nausea. It's important if you have this complaint
to avoid developing a state of shock by limiting the affected
areas.
Solar urticaria can affect both sexes and
may occur at any time of life.
Although this is not clearly understood,
it seems that a chemical is created in the body that reacts
to light, producing an allergic reaction which shows as urticaria.
The initial trigger for this condition is unknown.
Solar urticaria sometimes develops in patients
who are taking a drug (aspirin and morphine-like medicines)
or are exposed to a particular chemical. By avoiding contact
with these agents, the condition may resolve.
Usually, a doctor diagnoses the condition,
often using phototesting (where an instrument studies the
effects of light on the skin) and blood tests to confirm the
diagnosis.
Different doses of ultraviolet and visible
wavelengths are shone (usually on the skin of the back) to
measure a person's sensitivity to each part of the light spectrum,
with the response compared to that seen in normal subjects.
To prevent:
# Avoid sunlight when possible, particularly
between the hours of 11am and 3pm.
# Use 'protective' clothing, such as a wide-brimmed
hat, long-sleeved cotton top, and trousers.
# Apply high-protection, broad-spectrum sun
barriers frequently.
# Antihistamine tablets can help to abolish
or partially induce a remission of the condition in 60 per
cent of subjects.
# Phototherapy or desensitisation phototherapy
can be used to artificially toughen the skin of those affected
by the condition. Patients are usually treated three to five
times per week, receiving a total of 15 exposures. The result
is skin thickening and pigmentation, which can improve a patient's
tolerance to light.
# Occasionally, specialised forms of treatment
are needed.
* Plasmapheresis - a technique in which some
of the patient's blood plasma is removed by machine and the
red blood cells are then returned to the patient's circulation.
This removes a circulating factor from the
blood that may be involved in causing the urticaria, and is
demonstrably present in a small proportion of patients. The
technique is still being evaluated and is not always effective.
* Medicines that suppress the immune system
- such as prednisolone (eg Deltacortril) and ciclosporin (Neoral)
may be effective but because of their potential side effects,
their use is restricted to the most severely affected people.
What
is Urticaria ?|Classification
of Urticaria|Chronic
Idiopathic Urticaria|Cholinergic
Urticaria|
Cold
Urticaria| Urticaria
causes|Traditional
Chinese Medicine and Urticaria|Pressure
Urticaria|
Solar
urticaria
|
