Can Anti Tb Medicine Cause Side Effect?

my son got severe stomach infection from 7th month...for every 15days starting with often stooling and then vomitting..Dr gave antibiotic,but not cured..weight not incr properly..but no severe cold and fever..thn Dr suggested all test including Primary complex...its positive..but 10mm or less only...he gave medicine...after started that no stomach problem,,but cold and fever comes every month..now he is 15 months..he taking med for last 4 and half months...my doubt is BCG vaccine also makes primary complex test positive?(i studied in net) if yes means taking this anti TB medicine cause any side effect in my son body...like liver prblm etc.. now we came to dubai from india..here he is ok..no cold or fever...