To analyze the synergistic effects of applying lavender aroma to a footbath, we analyzed the EEG and emotional responses of footbath, lavender inhalation, and lavender footbath in women in their 30s. Foot baths reduced wave activation, wave and wave inactivation, and SEF50 and SEF90. The foot bath activated waves by about 66% compared to the background EEG, and reduced SEF50 and SEF90 by 0.43 Hz-0.68 Hz and 3.7 Hz, respectively. Lavender inhalation activated α, β, and γ waves at a concentration of 1% or more, and inactivated θ waves. As the concentration of lavender inhalation increased, α waves increased and β and γ waves decreased. Lavender foot bath activates θ waves and α waves, and inactivates β waves and γ waves. Compared with the background EEG, the lavender foot baths reduced SEF50 and SEF90, which are the median frequencies of EEG power, 0.5 Hz and 3.4 Hz, respectively. Lavender showed a positive emotional response when applied to inhalation and foot bath. Lavender showed a positive emotional response when applied to inhalation and foot bath. When the lavender was inhaled at the concentration of 1~10% and the lavender foot bath was applied, the average preference index (API) showed 0.64~0.66 and 3.6 ± 0.6, respectively. Lavender oil has a greater synergistic effect on emotional reactions when applied to an aromatherapy bath than by inhalation. Lavender decreased SEF50 and SEF90 as the API increased. A lavender footbath was superior to lavender inhalation in both emotional and EEG responses, and was more relaxed and calming than a footbath. These results suggest that the aroma foot bath method, in which lavender is applied to a footbath, is more effective in terms of providing relaxation and calming than a footbath or lavender inhalation aromatherapy.