I received frottage ( naked genital rubbing ) with no penetration from a female who is confirmed as syphilis positive. 10 days later i am now having an itchy body and random red spots that come and go. when can i test for syphilis for conclusive test?

These symptoms are not syphilis; 10 days is too soon for any symptoms except chancre (genital sore at the exposed site). A negative blood test will show your symptoms aren't syphilis, but too soon to be certain about a new infection from this exposure. Without penetration it was very low risk for syphilis, but still reasonable to have a blood test in 6 weeks. You can expect it to be negative.

Syphilis is contracted by by being exposed to syphilitic lesion thru open wound, blood, damaged mucosa (lining of body) From your description this did not occur. Also your symptoms are not consistent with syphilis as cause- 10 days later. You should see your doc for the cause and then let her/him decide if you need the test. In future suggest you refrain from this if you know the person is positiv