Texas Vascular Plant Image Library (Poaceae) machine-generated listing ...Most people find it confusing and it is rather confusing even for experts. Allergies vs cold is a topic which could lead to confusion for most of the people. Knowing the difference in symptoms does help a lot in treating it but the causal substance should also be known for a better treatment of them. While the causal organism for cold is a virus which attacks the immune system and infects the respiratory system leading to symptom arousal as the organism multiplies in the cell. An allergen is a substance which may not be harmful but our body considers it harmful and starts the protective mechanism. Nearly anything could be an allergen for different people. Most commonly people are allergic to pollen, molds, dust, cigarette smoke, etc. It is not defined that what starts the allergic reaction in some people. Allergies become worse if they occur just after cold hence it is important that the treatment is done properly under an expert guidance.