My 6 year old has a very painfull bump underneath his foot. it looks blistery, swollen and red. a thick red stripe is starting to form. what can it be?

See physician: Red stripe may mean infection and must be seen urgently. This area may represent infection from a bug bite or foreign body. Be seen and do not take chances, .

Possible infection : If a red stripe is starting to form it could be an infection and i suggest getting him to his pediatrician asap. Check the area for heat and check his temp.