Final answer:
Common cold medicine can make you sleepy due to the presence of antihistamines which have a sedative effect. It's important to check the medication's label for these side effects.
Step-by-step explanation:
True, common cold medicine can indeed make some people sleepy. This side effect is particularly associated with antihistamines, a common ingredient found in many over-the-counter cold remedies. Antihistamines can have a sedative effect, leading to drowsiness or sleepiness. While different formulations and brands vary in their side effects, always check the label of the medication for potential drowsiness-causing ingredients.