Untreated allergic rhinitis and conjunctivitis can lead to complications involving your nose, sinuses, eyes and ears. You can have a decreased or lost sense of smell and taste, have recurrent sinus infections, complain of poor quality sleep, sleep apnea, fatigue, and difficulty concentrating. Chronic mouth breathing can often lead to orthodontic issues resulting in the need for corrective braces or other treatments. Swelling around the middle ear can lead to infections, including middle ear popping, pain, and decreased hearing. Severe eye allergy symptoms can impact your vision and be dangerous to the health of your eyes.