Hay fever (allergic rhinitis) and the common cold share symptoms like a runny or blocked nose and sneezing, but there are useful differences. Hay fever typically causes itching of the eyes, nose, throat, and roof of the mouth, watery eyes, and thin clear mucus. It often appears or worsens at predictable times, such as high pollen counts in spring and summer, and it does not cause a fever.
A cold is caused by a virus. It tends to come on gradually, may include a sore throat, mild aches, and sometimes a low fever, and the mucus may thicken and turn yellow or green over a few days. Colds usually settle within seven to ten days, whereas hay fever can persist for weeks or months as long as you are exposed to the allergen.
If symptoms last more than a couple of weeks, recur every year at the same season, or come with significant eye itching, allergy is more likely. A pharmacist or doctor can help confirm the cause and suggest appropriate treatment, and can advise testing if your symptoms are hard to control.