An allergy is an overreaction of the immune system to some stimulus. On this occasion I wondered: maybe my immune system is not overreacting, but merely reacting — possibly to the threat of infection by Toxoplasma gondii! Perhaps my cat allergy is just a sign that my immune system is more evolved than the immune systems of those who aren’t allergic and are therefore more susceptible to T. gondii infection.
Do cat allergies in fact protect sufferers against T. gondii? If so, are we, as a group, less likely to exhibit the personality traits associated with T. gondii infection?
If the answer to both questions is “yes,” we might expect to see a correlation between cat allergies and an increased likelihood to vote Democratic.