Telling the differences between allergies and a cold is often a matter of understanding the symptoms of each. From a purely medical standpoint, allergies are a histamine response to things a person is allergic to, like pollens, mold, or dust mites. Colds, on the other hand, are the body’s response to dealing with a virus, typically a set of hundreds of rhinoviruses. There may be similarities between the two, but the differences can help a sufferer understand how to best address these separate conditions.
One of the early differences between allergies and a cold is the onset of symptoms. Allergies generally occur quickly, with all symptoms, like runny nose, itchy eyes, and scratchy throat, happening within a few hours of exposure. Cold symptoms tend to develop over a few days. A person might one day have a slightly congested nose and a slightly scratchy throat, but it may take several days before these symptoms progress to a full-blown cold.
Nasal discharge can also signify one of the differences between the two conditions. Allergic nasal response tends to have a discharge that is clear or white, and fairly thin. In the early days of a cold, discharge is thicker, sometimes so thick it is difficult to clear the nose by blowing it. No matter the cause, continued nasal discharge that becomes thick brown, dark yellow, or green might indicate a sinus infection.
How long a person continues to have symptoms also can help determine if it is an allergy or a cold. Generally, a cold lasts for seven to 14 days. Allergies, especially seasonal ones, can last for three weeks to several months. Colds can occur at any time of year, but allergies to pollen are likely to occur most often in spring and fall.
Both allergies and colds can cause feelings of fatigue, headaches, sneezing, coughing and asthma. One of the differences is that colds from certain viruses may also cause slight fevers. Allergies, though they are often called hay fever, rarely cause fevers unless the sufferer has a sinus infection.
People might also notice that they can tell the two apart by the medications that relieve the symptoms. Decongestants can be used for either allergies or a cold, but antihistamines are designed for allergies. The allergy symptoms are likely to resolve quickly, and may not return until the sufferer is re-exposed to the allergens. An antihistamine may provide minor relief to cold symptoms, but it will not eliminate them.
Though similarities exist in these two conditions, recognizing the differences between allergies and a cold can help in preventing allergies. People who are prone to seasonal allergies often find that antihistamines can help them almost completely eliminate the symptoms. It’s much harder to prevent a cold, though good hand washing practices certainly help.