The nasal cavity is rich with blood capillaries. There are more capillaries per cm than in most organs of the body. Five arteries connect to the nasal cavity, while the Little’s area is a frequent site of nasal bleeding. Given the rich supply of blood and the thin, permeable membrane within the nasal cavity, the light can easily reach the blood. Thus, this area is well-suited for systemic photbiomodulation which via blood.