Oral blistering during fever is due to the following reasons: first, the most common factor is infectious factors, the localization of the oral cavity is particularly susceptible to bacterial, viral and especially herpes virus infections, herpes virus infections, the patient’s oral cavity will initially form a number of herpes, sometimes scattered, and sometimes clustered and fused together into a sheet. As the disease progresses, these herpes will break out, and the patient’s pain is more obvious. Secondly, the oral cavity is susceptible to fungal infections and secondary pathogen infections during fever, for example, anaerobic bacterial infections can also lead to blistering in the oral cavity. Third, if you take antibiotics and anti-inflammatory drugs when you have a fever, you will have an allergic reaction, and blisters will appear in the mouth when you have an allergic reaction. Fourth, if the fever in the oral cavity lack of B vitamins, vitamin B2 serious lack of clinical symptoms can also lead to blistering in the oral cavity.