The trick to tasting a wine is a matter of aftertaste.

Let's do an exercise! Take a lemon, an orange and a tangerine. Squeeze them and divide the juices into three different glasses. At this point, plug your nostrils and taste them one after the other... above all, try to distinguish them and give each of them the fruit they belong to. It will be extremely difficult... you probably won't make it. Why?
Simple, you are tasting using only the senses of the mouth, so you will only perceive the acidity on the extreme sides of the palate and, perhaps, for orange and tangerine, even the sweet sensation on the tip of the tongue. But you don't have the perception of the aromas that make you distinguish the types of citrus fruits.
What is needed is the so-called 'aftertaste', that is, the nasal cavity. In fact, if you clear your nose, when you swallow the volatile and light aromas rise up the nasal septum and hit the mucous membranes that will discriminate the various scents, recalling the memory that we created ourselves since childhood.

So if we have a cold it's not worth tasting. And this applies not only to wines, but to all the products we ingest. The aftertaste is important in wine because it defines the most sensitive aromatic characteristics such as the scents of red fruit for red wines, the sensation of peach or apricot in white wines, the sensation of wildflower honey and toasted almonds in some Pantelleria passito.

So it's forbidden to catch cold before tasting... even if in the end we drink many times to warm up!

Fabio De Vecchi