Famciclovir
"Fabulous .. suffered cold sores all my life from that first kiss unbeknown . I spoke with my GP about it she even suffered them too , we did not know they existed I guess the boys didn't either . In my 54 years this is the first year I can say that I have a drug that actually works . I also carry aciclovir tube of cream with me everywhere normally I put it on at night . 
Maybe I get immune to it but anyways last night I didn't use it and this morning one big cold sore had appeared. Just taken the dose of FAMCICLOVIR ONCE 3 tablets one dose .. I know it'll be fine now too .. I used it before in my travels in oz where I bought it originally costing about £25 maybe expensive but so so worth it."