When suffering from an excess of cold earthy humours, leading to an excess of phlegm (i.e. a cold) it is suggested that heating drying foods should be consumed, so as to balance the body.
Luckily both lemon and honey neatly fulfill these demands.
Annoyingly my list of where foods sit in the Hippocratic schema is lacking a listing for whisky, however I cannot envisage of it being regarded as anything other than a panacea, especially in how it combines all four of the principal humours. Being at once warming, while still evoking the ancient chill of the Caledonian hills. It’s almost unique ability to slake thirst and yet dry the body out at the same time fulfills the other two humours, thus neatly replacing the vinegar which completes the classic oxymel compound.
Therfor, we can safely say that the hot toddy, or Oxmel to give it it’s medicinal name is proven (so long as you work on a two and a half millennia old, and discredited, theory of medicine) to rebalance the body and cure one of a cold.