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Porphyria Educational Services

Vol. 2 No. 2                                            January 9, 2000
FOCUS: Wood's Lamp Test for Porphyria

The old-fashioned black light test, also known as the ujltraviolet
light test, today is known as the Wood's Lamp Test for Porphyria.

The  test is performed in a dark room where ultraviolet light is
shined on the area of interest to detect the presence of
 infectious organisms which contain substances that glow on
the skin in the presence of ultraviolet light.

The patient is usually seated, and the lights will be turned off.
After the patient's  eyes adjust to the darkness, the Wood's lamp
is turned on and held 4 to 5 inches from the area being studied.
The patient should be careful not to look directly into the light.

The test involves sitting while your physician  focuses the ultraviolet
light over the skin being studied.

There are no risks to the Wood's Lamp Test, but the patient should
 avoid looking directly into the ultraviolet light, just as the patient
 would avoid looking into the sun.

The test is performed for many different diseases, among them porphyria.
Other diseases include: scabies,  bacterial infections, fungal infections,
and pigmentary alterations.

Normally your skin will not fluoresce, or shine under the ultraviolet light,
however with certin types of porphyria the skin will shine.

Washing before the test may cause a false negative result.
A room that is not dark enough may also alter results.
Several other materials may alter results. Such things may include
facial creams, deodorants, make-up, tetracycline and soaps
in the sweat which may fluoresce.

Some species of tinea capitis lack porphyrins and therefore will not

The abnormal results of the Wood's Lamp Test which is done
under the ultraviolet light, show different infections and
conditions of which show different colors:

golden yellow (Tinea versicolor)
pale green (trichophyton schoenleini)
bright yellowgreen (Microsporum audouini or M. canis)
aquagreen to blue (Pseudomonas aeruginosa)
pink to pinkorange (Porphyria cutanea tarda)
ash-leaf-shaped spot (Tuberous sclerosis)
bluewhite (Leprosy)
pale white (hypopigmentation)
purplebrown (hyperpigmentation)
cold, bright white, or bluewhite (depigmentation, vitiligo)
cold, bright white (albinism)
coralred, pink (erythrasma)

How to prepare for the test
It is most important not to bathe or shampoo for 24-hours
before your test, because porphyrins (a substance found
in the suspect organisms) are removed with soap and water.