The cause of a very dry mouth needs to be analyzed and not just oral vitamins. A very dry mouth can be caused by vitamin deficiency, pathogenic bacterial infections, allergies and other factors. For different causes, vitamins, anti-infection, anti-allergy and other treatments can be given. 1. Lack of vitamins: lack of vitamins can easily lead to the symptoms of dry skin and mucous membranes, long-term will make the skin become sensitive, increase the prevalence of lipitis, mouth ulcers and so on. It is recommended to take vitamin B2, vitamin A or vitamin c to help repair the mucous membranes and promote sebaceous gland function. 2. Pathogenic bacterial infections: most commonly caused by Candida, staphylococcus infections, followed by lipitis, stomatitis and so on. For this situation, the treatment should be localized with antibiotics (such as erythromycin ointment) local application, if necessary, oral broad-spectrum antibiotics (such as cephalosporin, penicillin, etc.). 3. Allergy: lips contact allergens, the formation of chronic allergic inflammatory reaction. If the inflammation does not recede repeatedly, or lead to dryness of the skin stratum corneum and mucous membrane of the lips, in this case, it is recommended to remove the allergens, under the guidance of a doctor, the rational use of anti-allergy drugs, such as chlorpheniramine, loratadine, etc.. In short, when there are dry lips and other conditions, it is recommended to go to the hospital in time to find out the cause of the disease, under the guidance of the doctor for drug treatment, do not unauthorized use of drugs.