Allergic rhinitis happens when your immune system reacts to something harmless in the environment, like pollen, dust mites, mold, or pet dander, as if it were a threat. Your body releases histamine and other chemicals in response, which leads to sneezing, a runny or stuffy nose, and itchy, watery eyes.
It can happen seasonally, often called hay fever, or all year round if you're exposed to the trigger regularly, such as dust at home. It's very common and usually manageable, though it can affect sleep, concentration, and overall quality of life if left untreated.