Protection afforded by sunscreens containing inorganic sunscreening agents against blue light sensitivity induced by aminolevulinic acid.
BACKGROUND
Application of aminolevulinic acid (ALA) for photodynamic therapy induces significant sensitivity to visible light.


OBJECTIVE
To determine whether sunscreens containing inorganic agents are effective against sensitivity to blue light induced by ALA application.


METHODS
Twenty subjects received application of ALA on the arm. Thirty minutes before blue light exposure, two sun protection factor 50 inorganic-based sunscreens containing iron oxide 3.2% and 0.2% were applied on separate areas where ALA was applied; a third area received no sunscreen. Small areas of skin were exposed to increasing fluences of blue light 3 or 18 hours later, and the minimal phototoxic dose (MPD) was noted.


RESULTS
Three hours after ALA application MPD was 29.2 and 22.6 J/cm(2) for skin protected with sunscreen containing iron oxide 3.2% and 0.2%, respectively, and 10.6 J/cm(2) for unprotected skin (p=.003 and .0497 respectively). At 18 hours after ALA application, MPD for sunscreen containing iron oxide 3.2% was 5.78, compared with 0.33 for unprotected skin (p<.001) with a blue light protection factor of 21.


CONCLUSIONS
The sunscreen containing iron oxide 3.2% afforded significant protection against blue light sensitivity induced by ALA application.
Bissonnette
Robert
R
Innovaderm Research Inc, Montreal, QC, Canada. rbissonnette@innovaderm.ca
Nigen
Simon
S
Bolduc
Chantal
C
Méry
Sophie
S
Nocera
Thérèse
T
D000328:Adult; D000622:Aminolevulinic Acid / Q000009:adverse effects*; D017454:Dermatitis, Photoallergic / Q000209:etiology* / Q000517:prevention & control*; D005260:Female; D005290:Ferric Compounds; D006801:Humans; D008297:Male; D008875:Middle Aged; D017319:Photosensitizing Agents / Q000009:adverse effects*; D013473:Sunscreening Agents / Q000627:therapeutic use*; D014025:Titanium; D015034:Zinc Oxide
D005290:Ferric Compounds; D017319:Photosensitizing Agents; D013473:Sunscreening Agents; C009495:titanium dioxide; C000499:ferric oxide; D000622:Aminolevulinic Acid; D014025:Titanium; D015034:Zinc Oxide