Tongue redness and pain when eating can be caused by improper diet, lack of trace elements, fungal stomatitis and so on. 1. Improper diet: If you eat a lot of spicy and stimulating or high-temperature food at one time, it will stimulate the tongue mucosa, which will cause the tongue to become red and painful. 2. Lack of trace elements: long-term existence of partiality, picky eating and other bad eating habits, resulting in the lack of zinc, iron and other trace elements and folic acid, vitamin B and other vitamins, will also appear in the tongue mucous membrane ulcers, which can lead to redness, swelling and pain in the tongue. 3. Fungal stomatitis: daily do not pay attention to oral hygiene, when the body immunity is low, it is easy to oral fungal infections, this situation will induce fungal stomatitis, can be manifested as tongue redness, swelling and pain, and accompanied by local oral mucosa swelling and congestion. Normally, we should pay attention to improve the bad dietary habits, try not to eat spicy stimulating food, after meals, we should actively rinse the mouth, brush the teeth, maintain oral hygiene. In order to clarify the diagnosis, it is recommended to go to the hospital stomatology department in time, so as not to delay the condition.