[sokoloff]

Having your SOP for dealing with a cold being "select exactly one box from your medicine cabinet [or pharmacy shelf] and take the recommended dose" is likely to produce fewer unwanted interactions than if your SOP is "select 1 to N boxes from your medicine cabinet and take the recommended dosage of each of those medications", especially when the person selecting is far from their peak mental performance due to the cold symptoms they're experiencing.

Many (likely most males under 60) people take zero pills on a given day when not sick.