Dabs are not much different than hash. THC trichomes are simply separated from. The plant matter. Hash usually with cold straining, honey oil (what a dab really is) uses either butaine or alcohol. Obviously dabs are more "pure" in THC. Dabs take far less "matter" to get you high. Hence the term dab, cause a dab.will do ya. Most people partake in a dab much like they are smoking a bowl. Which is why they get sick feeling. They do to much to fast. Think if a dab as more of a fine scotch if you will. Sip it, don't slam it.
As for medicinal side, it all stems from the THC. There are two forms of cannabinoid. One is responsible for the high, pain relief. The other is the medicinal, anti seizure, ect. Neither can be over dosed on. If you smoke too much, you will feel like ****, then eventually become, "stoned sober." When the cannabinoid receptors in the brain become over flown with THC, it will release a countering chemical that flushes the repectors. This is how you smoke yourself straight.