Researcher: Research has shown that inhaling the scent of lavender has measurable physiological effects tending to reduce stress. It is known that intense stress can impair the immune system, making one more susceptible to illness. Ttherefore, it is likely that the incidence of illness among those who regularly inhale the scent of lavender is reduced by this practice.
At least some people who use the scent of lavender to induce relaxation and reduce stress are no more susceptible to illness than average is an assumption that the researcher's argument requires.