Intranasal systemic photobiomodulation is the utilization of light energy within the 620nm-750nm (red light) range on the electromagnetic spectrum to irradiate the capillary-rich nasal cavity.
Red light has less penetrative potential than near infrared light (750+nm), therefore a majority of the photons do not bypass the blood capillaries but are absorbed instead.
The tissue around the nasal cavity has abundant blood capillaries with relatively slow blood flow. Intranasal photobiomodulation improves oxygenation and leads to increased adenosine triphosphate (ATP) levels in various tissues. 
Light energy absorbed by blood through the photobiomodulation process leads to an increase in nitric oxide (NO) release.
Nitric oxide is one of the most important factors affecting microcirculation. This leads to increases in vasodilation which contributes to improved oxygen delivery to tissues – which is important for optimizing your health and sports performance.
The result of light-induced photodissociation of oxyhemoglobin also results in significant enrichment of local tissue oxygenation. 
The systemic effect of photobiomodulation on circulation could be a consequence of positive alterations in the membrane properties of red blood cells (RBCs). Absorption of red/NIR light affects hydrogen bonds, which could induce structural changes in RBC membrane proteins. 
This in turn, results in an improvement of RBC structure, ATP content and osmotic properties. 
 – Pitzschke, Andreas & Lovisa, B & Seydoux, O & Zellweger, M & Pfleiderer, Martin & Tardy, Y & Wagnières, Georges. (2015). Red and NIR light dosimetry in the human deep brain. Physics in medicine and biology. 60. 2921-2937. 10.1088/0031-9155/60/7/2921.
,  – Lohr NL, Keszler A, Pratt P, Bienengraber M, Warltier DC, Hogg N. Enhancement of nitric oxide release from nitrosyl hemoglobin and nitrosyl myoglobin by red/near infrared radiation: potential role in cardioprotection. J Mol Cell Cardiol. 2009 Aug;47(2):256-63. doi: 10.1016/j.yjmcc.2009.03.009. Epub 2009 Mar 25. PMID: 19328206; PMCID: PMC4329292.
 – Stadler I, Evans R, Kolb B, Naim JO, Narayan V, Buehner N, Lanzafame RJ. In vitro effects of low-level laser irradiation at 660 nm on peripheral blood lymphocytes. Lasers Surg Med. 2000;27(3):255-61. doi: 10.1002/1096-9101(2000)27:3<255::aid-lsm7>3.0.co;2-l. PMID: 11013387.
 – Szymborska-Małek K, Komorowska M, Gąsior-Głogowska M. Effects of Near Infrared Radiation on DNA. DLS and ATR-FTIR Study. Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jan 5;188:258-267. doi: 10.1016/j.saa.2017.07.004. Epub 2017 Jul 12. PMID: 28723592.
 – Walski T, Dyrda A, Dzik M, Chludzińska L, Tomków T, Mehl J, Detyna J, Gałecka K, Witkiewicz W, Komorowska M. Near infrared light induces post-translational modifications of human red blood cell proteins. Photochem Photobiol Sci. 2015 Nov;14(11):2035-45. doi: 10.1039/c5pp00203f. PMID: 26329012.