The most common reason is allergic rhinitis, because there is hot steam inside the meal, the hot steam stimulates the nasal mucosa, and the runny nose under the stimulation usually belongs to the sign of allergic rhinitis, and the runny nose is clear, not mucus or pus-yellow nasal discharge. 2. In the case of acute rhinitis, the alternation of hot and cold air can cause nasal sensitivity during meals, resulting in a runny nose and obvious yellow nasal discharge.