Passage Summary: Allergies cause your body to release a chemical called histamine that makes you feel sick, and while medicine can block it, that medicine also makes you sleepy; notably, colds don't use histamine at all.

Reasoning: Allergens trigger histamine release which causes nasal symptoms; antihistamines block histamine to treat these symptoms but also cause drowsiness; however, histamine is not involved in cold symptoms.

Analysis: Since this is a 'Must be True' question, we are looking for a logical deduction based on the provided facts. The most significant connection here is that antihistamines work by blocking histamine, yet colds do not utilize histamine to produce symptoms. Therefore, it is highly probable that antihistamines will not effectively treat the symptoms of a cold, even if they still cause the side effect of drowsiness. Focus on an answer that synthesizes these two distinct biological pathways.