👉 Aphtha is a condition in which the phlegm, or mucus, that normally lines the inside of the nose and throat can become thickened and obstructive. It can be caused by various factors such as allergies to pollen, dust, or other irritants, smoking, alcohol consumption, certain medications, or even stress and fatigue. The symptoms of aphtha include difficulty breathing, coughing up mucus, sneezing, and a sense of fullness in the throat. Treatment