Outdoor allergens often trigger swelling in the sinuses (air-filled pockets found within the bones of the nose and face) and in the passage leading from the throat to the middle ear. Because of this, the most common symptom associated with outdoor allergens is frequent and prolonged sneezing. Other common symptoms may include:

• Itchy and runny nose
• Congestion
• Redness, swelling and itching of the eyes
• Itchy and sore throat
• Coughing
• Ear infections and itchiness in the ears
• Sinus infections

In some cases, outdoor allergens can cause anaphylaxis, which is an allergic reaction that involves two or more body systems. Anaphylaxis can lead to the potentially life-threatening anaphylactic shock which involves a dangerous drop in blood pressure and breathing difficulties.

The symptoms related to outdoor allergens often vary in severity depending on the individual and the environment. However, they will usually last throughout an entire season (with seasonal allergic rhinitis) or throughout the entire year (with perennial allergic rhinitis). The most severe cases are considered extremely uncomfortable and can make it difficult to carry out even normal everyday tasks.