Multiple chemical sensitivity (MCS) is a controversial, complex, and recurring chronic disturbance resulting from olfactory exposure at low levels to foreign chemicals usually tolerated in the rest of the healthy population, without functional tests capable to explain signs and symptoms of the disorder. Recently, some authors have supported that organic abnormalities in the olfactory sensors and a hyperactive limbic system, combined with peculiar personality traits, can best explain MCS. Epidemiological observations suggest that MCS has a 2-3% prevalence in the general population and that women are more significantly at risk to develop the disturbance; about 80% of affected patients are in fact women between the ages of 30 and 50. On closer inspection, many women present with hyperosmia during two other common female conditions, i.e. pregnancy and menstrual migraine, both accompanied by well known neurovegetative limbic symptoms; therefore, it appears reasonable to include a hormonal imbalance in the pathogenesis of MCS.