The experiment investigated the effect of light wavelength upon salivary secretion and cutaneous temperature of the
foot in humans. Seven healthy young female students served as participants. They spent three nights in a bioclimatic
chamber controlled at 26 °C and 60%. Participants were exposed to two different wavelengths of light from 1800 to
2400 h on second day and third day: 1) Fluorescent light (FL) with short wavelengths and a high color temperature
(6,500 K); 2) Incandescent light (IL) with long wavelengths and a low color temperature (3,000 K). Light intensity
was 400 lx in both conditions. Saliva was collected every 10 min from 2100 to 2200 h, and from 2300 to 2400 h on the
second and third days, by a Lashley cup fixed to the parotid gland. The mean salivary secretion rate between 2100
and 2200 h was 15.27±2.86 g/h (Mean±SEM, N=7) in the IL condition and 10.80±2.97 g/h in the FL condition
(p<0.011) and, between 2300 and 2400 h, 14.98±3.80 g/h in the IL condition and 11.55±2.60 g/h in the FL condition
(p<0.057). Foot skin temperature was significantly higher in IL than FL during the period 1800–2400 h. These findings
suggest that the parasympathetic nervous system, which is responsible for serous saliva flow, is less suppressed
by IL condition, and that the sympathetic nervous system, which is responsible for vasoconstriction of foot skin vessels,
is less activated by IL
