In theory, genital herpes can be transmitted by genital apposition without penetration ('outercourse'), but it's very rare if it occurs at all. I have never seen a case in my 35 years in the STD business. And many things other than herpes can cause the sort of genital itching you describe; a yeast infection probably is the best bet and much more likely than herpes. But see a health care provider if the symptom continues or you otherwise remain concerned.
Good luck-- HHH, MD
Just about everybody has occasional genital area itching, usually without explanation. But I repeat that to know for sure, you should visit your health care provider, preferably when you are having the symptom. But until then, you can safely disregard herpes as a possibility.