I Have Just Taken One Keflex Tablet Prescribed For An

I have just taken one keflex tablet prescribed for an infected serbatious cyst within one hour I had severe diarrhoea followed by violent vomiting I have taken a maxolon which has stopped the vomiting. I have also has this same reaction with augumentin forte. I need to clear up this infection as travelling overseas in 4 days ?? Any suggestions for an alternative antibiotic