I believe the op is referring to "wax" as in a Cannabis
concentrate somewhat waxy in texture, usually made using butane
or oxygen supercritical. Very potent.
By "Green Crack
" I believe they are referring to the Sativa dominant Cannabis strain Green Crack.
As for the symptoms experienced, anxiety is probably the culprit. I have a medical cannabis reccomendation so am able to visit Cannabis dispensaries as well, and the wax is always a favorite, however I tend to use ALOT more than a "dab"
Though if a person is only used to "half a dab" or so, especially with such a potent concentrate and a soaring heady Sativa strain to boot, then one might experience some negative effects yes. Maybe a panic attack
as was mentioned. I have noticed similar effects on occassions when i was unable to medicate(as I like to call it) for a day or two and tolerance drops slightly then take 1 toke too many