Aim:
Background: Circadian rhythms' is a pivotal role in controlling various functions and activities of body organs and systems. It may affect the functions of certain glands in the body, such as salivary glands. Aims: evaluate the effects of constant light on the histological, histomorphometric and expression of EGFR of sublingual.

Material and methods:
Materials and methods: 20 male mice were applied and classified in to Group (A) was kept in continuous light and control group (B) was kept in the normal daily variance for 45 days.

Results:
Results: group A changes in behavior they become irritable, aggressive, loss of appetite, lethargic& lose weight. Histological examination with H&E showed degeneration of the sublingual tissue, loss architecture and necrosis (acini and ducts), the distraction of cell membrane and vacuolization, loss of nuclei in the necrotic tissue about 60%. Histomorphometric revealed significant differences in acini diameter between groups (p≤0.001). The mean of group A was (116.5960± 3.41668) compared with B group was (340.2720 ± 6.95821). Immunohistochemistry technique by used EGFR antibody in group A revealed expression evaluated as (0.8362±0.00822) increase in values in comparison with group B (0.6988 ± 0.02489).

Conclusions:
Conclusion: Light has an indirect oxidative stress effects that causes oxidative damage to glands, which affects mucin secretion. Therefore, there was a decrease in diameter of acini sublingual glands of light group than control group, however, there was increase in the expression EGFR of sublingual glands in light group compare with control group as compensatory mechanism for oxidative stress in glands by light.