This study is being done to compare a new, continuous illumination and short Incubation time
regimen of 5-aminolevulinic acid photodynamic therapy (painless ALA- PDT) to low-dose and
conventional dose of oral isotretinoin for treatment of moderate or severe acne vulgaris. The
hypothesis is that the painless ALA- PDT will be equally or more efficacious as oral
isotretinoin, and taking effect more quickly with less adverse effect.