Light treatments of sebaceous gland disorders with 5-aminolevulinic acid and photodynamic therapy are disclosed. A preferred treatment includes topical application of 5-aminolevulinic acid to the skin followed by light exposures with repeated treatment at various intervals. At low doses of ALA and photodynamic therapy (PDT) in single or multiple treatments, improvement in the sebaceous gland disorder, e.g., acne, provides the discovery that diminishment in sebum secretion and the eradication of bacteria occurs. At high doses of ALA and a single high energy PDT treatment, permanent changes to the sebaceous gland and sebum secretion have been discovered.