Harvard Health Tips
Bad cold vs. allergy
Allergy symptoms may be similar to those of a cold or the flu. But while viruses do cause colds and the flu, they do not cause allergies; malfunctions of immune system cells do. Therefore, antihistamine allergy medications won't do much for your cold. Decongestant allergy medications have slight temporary effectiveness when used for the first time, but they will not be effective long term.