Ukwelashwa ngokukhanya bekulokhu kukhona kusukela izitshalo nezilwane zisemhlabeni, njengoba sonke sizuza ngezinga elithile elangeni lemvelo.
Akukhona nje kuphela ukuthi ukukhanya kwe-UVB okuvela elangeni kuhlangana ne-cholesterol esikhumbeni ukusiza ekwakheni i-vitamin D3 (ngaleyo ndlela kube nenzuzo yomzimba wonke), kodwa ingxenye ebomvu ye-spectrum yokukhanya okubonakalayo (600 - 1000nm) ixhumana ne-enzyme ebalulekile ye-metabolic ku-mitochondria yeseli lethu, okuphakamisa isivikelo emandleni ethu okukhiqiza amandla.
Ukwelashwa kokukhanya kwanamuhla bekulokhu kukhona kusukela ngasekupheleni kwawo-1800, ngemuva nje kokuba ugesi nokukhanyisa ekhaya sekuyinto evamile, lapho uNiels Ryberg Finsen, owazalelwa eFaroe Islands, ezama ukukhanya njengendlela yokwelapha izifo.
Kamuva uFinsen waqhubeka nokuwina umklomelo kaNobel wezokwelapha ngo-1903, unyaka owodwa ngaphambi kokufa kwakhe, ephumelela kakhulu ekwelapheni i-smallpox, i-lupus nezinye izimo zesikhumba ngokukhanya okuqinile.
Ukwelashwa kokukhanya kwasekuqaleni kwakuhilela kakhulu ukusetshenziswa kwama-incandescent bulbs endabuko, futhi kuye kwenziwa izifundo eziyi-10,000 ngokukhanya phakathi nekhulu lama-20. Izifundo zisukela emiphumeleni ezimpethu, noma ezinyonini, kwabesifazane abakhulelwe, emahhashini nasezinambuzaneni, kumagciwane, ezitshalweni nokunye okuningi. Intuthuko yakamuva kwaba ukwethulwa kwamadivayisi e-LED nama-laser.
Njengoba imibala eminingi yayitholakala njengama-LED, futhi ukusebenza kahle kobuchwepheshe kwaqala ukuthuthuka, ama-LED aba ukukhetha okunengqondo kakhulu nokuphumelelayo kokwelashwa kokukhanya, futhi kuyindinganiso yemboni namuhla, kanti ukusebenza kahle kusathuthuka.