Hi. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns... As per your complain it seems that your son is suffering from HERPATIC GINGIVOSTOMATITIS which is a viral infection and can lead to fever, swollen gums and bad breath and in a day or two there can be outbreaks of blisters in and around the mouth known as cold sores.. all the symptoms that you explained are completely pointing towards herpes virus infection.. It is a contagious infection and the child may get it from kissing , eating or coming in contact with people who have active infection.. The initial treatment is directed towards reducing fever and decreasing the discomfort caused due to inflammation in mouth.. You should feed your son with a soft ,cold and bland diet, a low spice vegetable soup, flavoured gelatin, bread socked in milk etc can be given.. Avoid citrus juices like orange juice and can give him fresh apple juice.. For fever you can give him Tylenol or Acetaminophen .. Application of a numbing gel like Lignocaine over the gums and other sore areas of mouth can provide relief, but care should be taken not to involve large areas of mouth as when being numb the child can accidentally bite the tongue and also damage other areas of mouth unknowingly.. Sucking ice pops or a frozen apple juice popscicle can help in reducing inflammation and discomfort... Maintain a good oral hygiene and use an ultra soft toothbrush for brushing can help by preventing trauma and pain to gums.. In case if there is an outbreak of sores or blisters antiviral medicines like Acyclovir can be advised by a Paediatrician to reduce the duration of the disease and prevent further outbreaks.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora..