Swollen mouth can be caused by allergy, lipitis, urticaria, contact dermatitis, etc. 1. Allergy:In life, if you are allergic to a certain food or something, after consuming or making contact with the allergic substances, it will lead to redness and swelling of the mouth, accompanied by itching of the skin and other symptoms. 2. Lipitis: when affected by climate, sun exposure, drugs, food and other factors, can lead to the appearance of lipitis, the patient is mainly manifested as swelling, lip flaking and so on, accompanied by itching, vesicles and so on. 3. Urticaria: when affected by food, drugs or other factors, leading to temporary expansion of small blood vessels in the skin and mucous membranes, triggering the swelling of the mouth, the skin will appear in varying sizes of lumpy elevations, accompanied by obvious itching. 4. Contact dermatitis: swollen mouth may be caused by contact dermatitis, when the skin or mucous membranes in contact with external pathogenic substances, will cause the appearance of this situation, mainly manifested as erythema, papules, blisters, itching and other symptoms. It is recommended that patients go to the regular hospital in a timely manner, under the diagnosis of the doctor, according to the patient’s condition, to take targeted treatment, life to avoid contact with irritants, pay attention to protection.