Background: Infrared irradiation stimulates collagen production, but histological differences in its long-term effects on type I versus type III collagen and elastin in human tissue are unclear.

Objective: To investigate the effects of infrared irradiation.

Methods and materials: In vivo human tissues in sun-protected and sun-exposed areas were irradiated with infrared. Histological samples were analyzed, and visual changes were assessed up to 90 days post-treatment.

Results: Infrared irradiation provided long-term increases in collagen and elastin levels on post-irradiation days 30, 60 and 90 compared to controls. Significant increases in type I collagen persisted until 30 and 60 days, and in sun-protected and exposed skin biopsies, respectively. Significant increases in type III collagen and elastin persisted until 90 days in both sun-protected and sun-exposed skin biopsies.

Conclusion: Infrared irradiation provides safe and effective long-term stimulation of collagen I and III and elastin, which is beneficial for improving skin laxity and wrinkles.

Tanaka Y, Matsuo K, Yuzuriha S. Long-term evaluation of collagen and elastin following infrared (1100 to 1800 nm) irradiation. J Drugs Dermatol. 2009 Aug;8(8):708-12. PMID: 19663107.