Hah! Preventive medicine, indeed. I think I feel winter coming on...

I'd say that the essential ingredients are boiling hot water, hard liquor*, lemon, and honey (preferable to sugar).

Adding some kind of aromatic spice like clove, nutmeg, ginger, cinnamon, etc., is probably a plus because it'll clear your sinuses.

I throw in a teabag myself sometimes (especially mornings when I'll be staying home sick), but I suspect that brewing tea into a hot toddy might be counterproductive, because the water inevitably cools down during the brewing process. Maybe it's better to omit the tea and get the stuff into yourself while it's still really hot.

* While I may *prefer* Irish whiskey as the "active ingredient," with dark rum a close second, I can't believe it makes much difference if you use rye or bourbon or Scotch instead, or even (horrors!) gin or vodka. For most people, whatever liquor they like best will be what's most often available in their house, and that should be good enough.