If i got a vaginal outbreak from an hsv1 person who had a coldsore and gave me oral sex is it possible my blood test could be negative?

Viral Testing: It depends on when the test was taken. It can take several weeks to several months for a viral blood infection to be positive on blood testing.

Absolutely: Since it takes time to develop antibodies--it depends when you were exposed and how soon afterward you were tested. If you have had exposure to hsv, the initial 'illness' will be an inflammatory outbreak. A 'cold sore' can occur subsequently, when the immune system is challenged by illness, medications, etc. Be aware, cold sores actively shed the virus--highly infectious.