Cold Urticaria (essentially meaning cold hives ) is an allergy where hives or large red welts form on the skin after exposure to a cold stimulus. How Can I Tell if I Have Seasonal Allergies or a Cold? A cold will usually last two weeks or less. They can last longer, but typically clear up within two weeks. Allergy testing involves having a skin or blood test to determine what substance, or allergen, may trigger an allergic response in a person. Get the facts on treatment of the common cold, influenza, and allergy symptoms (headache, fever, sneezing, cough, sore throat) with over-the-counter (OTC) medications. Characteristic. Cold. Allergy. How Long It Lasts. 3-14 days. Days to months -- as long as you're in contact with the allergy trigger. When It Happens. Most often in. My son has been sneezing for the past few weeks and blows his nose constantly. How can I tell if he has allergies or just a lingering cold? - Michelle Learn how to tell the difference between common cold and allergy symptoms. Effective management of allergic diseases relies on the ability to make an accurate diagnosis. Allergy testing can help confirm or rule out allergies. Codeine and hydrocodone are narcotic oral cough suppressants that require a doctor's prescription. Dextromethorphan is an oral cough suppressant that is available OTC. Cold urticaria may also be caused by a number of underlying medical problems, including a variety of infections, autoimmune diseases, some cancers, and side effects.