1. Itchy, watery eyes
Airborne allergens come into direct contact with your eyes. Over 80% of people with allergies experience this symptom.
2. Runny nose
When allergens enter your nose, your immune system releases chemical that can make the blood vessels in your nose swell causing them to expand. This allows the fluid to come out into the nose as thin, clear, watery liquid.
Your body’s reaction to histamine includes itchiness and swelling inside your nose and throat. As a result, there is irritation of your nasal passage and some obstruction in your ability to breathe through your nose. This will trigger nerves in your nose to send a signal to your brain to which it responds with your sneeze reflex to help clear the irritation or obstruction.
4. Itchy nose or throat
Itchy nasal passages are also a reaction to the release of histamine triggered by an allergen in your system. Histamine interacts with the nerves in the nasal passage which reacts by causing the itching.
5. Sinus congestion
If your allergies include upper respiratory symptoms – sneezing, itchy and runny nose – your sinuses may become swollen and blocked as the nasal passage branches into your sinuses, which make them prone to the same reaction as your nasal passage.