Objectives This study aimed to investigate the effect of cortisol, estrogen, and nicotine on heat shock protein 70 (HSP70) expressions at the level of normal oral mucosa keratinocyte cells. Methods In this in vitro study, keratinocytes were derived from rat oral cavity and cultured. Stressors were applied, including three groups, group 1: estrogen to simulate the postmenopausal state; group 2: cortisol to simulate psychological stress situation; group 3: nicotine to simulate smoking state. To determine the exact nature of keratinocyte cells, two surface markers, cytokeratin 18 and cytokeratin 14 were examined using the flow cytometry method. Then, the immunocytochemistry technique with three repetitions in each group was used to evaluate the HSP70 expression before and after applying the stressor. Results HSP70 expressions in the three stressor groups (estrogen, cortisol, and nicotine) were significantly lower than in the control group (p = 0.0001). The HSPs expression difference between cortisol and nicotine was statistically significant (p = 0.0001). Based on the results of MTT analysis, the mean cell viability of oral mucosal keratinocytes in all three intervention groups decreased compared to the control group. In the cortisol and nicotine groups, cell death was significantly higher than in the control group. In the estrogen group, cell death was significantly lower than in the nicotine group (p > 0.05). Conclusions The specific concentrations of cortisol, estrogen, and nicotine as stressors can effectively reduce the expression of HSP70 in normal oral mucosal keratinocytes. These phenomena can be effective in cell viability and the development of oral lichen planus.