Well, with "erythema and edema", I was trying to evoke any sorts of unfavorable effects of needling, such as unnecessary bleeding. Interestingly, Follica's Dr. Dhurat responded to a patient's question saying you should never microneedle so much that you bleed. (It's on this forum.) Her statement is absurd, but on the other hand, why did she say that? (Is there something to it?) Another potentially unfavorable effect is crusting, as I keep asking myself, will the crust interfere with minoxidil absorbtion? (Even though I always shave my head before microneedling with the D2, it's very difficult to wash off all the blood or to not get any crusting.)
Rassmann is one doctor saying the needles should go from 1.0 to 1.5mm. He also refutes neogenesis, recommends microneedling on a daily basis rather than weeks apart, and never discusses any type of tools other than manual dermarollers. He seems a bit out of touch.