Topical
aminolevulinic acid is converted into a potent
photosensitizer,
protoporphyrin, in human hair follicles and sebaceous glands.
Photodynamic therapy with topical
aminolevulinic acid was tested for the treatment of
acne vulgaris, in an open-label prospective human study. Each of 22 subjects with
acne on the back was treated in four sites with
aminolevulinic acid plus red light,
aminolevulinic acid alone, light alone, and untreated control. Half of the subjects were treated once; half were treated four times. Twenty percent topical
aminolevulinic acid was applied with 3 h occlusion, and 150 J per cm2 broad-band light (550-700 nm) was given. Sebum excretion rate and auto-fluorescence from follicular bacteria were measured before, and 2, 3, 10, and 20 wk
after, treatment. Histologic changes and
protoporphyrin synthesis in pilosebaceous units were observed from skin biopsies.
Aminolevulinic acid plus red light caused a transient
acne-like
folliculitis. Sebum excretion was eliminated for several weeks, and decreased for 20 wk after
photodynamic therapy; multiple treatments caused greater suppression of sebum. Bacterial
porphyrin fluorescence was also suppressed by
photodynamic therapy. On histology, sebaceous glands showed acute damage and were smaller 20 wk after
photodynamic therapy. There was clinical and statistically significant clearance of inflammatory
acne by
aminolevulinic acid plus red light, for at least 20 wk after multiple treatments and 10 wk after a single treatment. Transient
hyperpigmentation, superficial exfoliation, and crusting were observed, which cleared without
scarring. Topical
aminolevulinic acid plus red light is an effective treatment of
acne vulgaris, associated with significant side-effects.
Aminolevulinic acid plus red light causes
phototoxicity to sebaceous follicles, prolonged suppression of sebaceous gland function, and apparent decrease in follicular bacteria after
photodynamic therapy. Potentially,
aminolevulinic acid plus red light may be useful for some patients with
acne.