If I have developed resistance to benadryl's sedating effects (+/-150mg), will it still work4allergy?

Give it a try. Diphenhydramine (benedryl) is a very effective antihistamine, holding on to histamine binding sites better than some products. Its drawback other than sedation has been its limited duration of effect, eclipsed by products like zyrtec (cetirizine) that can last all day. Sedation is not a measure of its worth, only its ability to get into your brain and mess with neurotransmitters.
Yes..but. First generation antihistamines like Benadryl (diphenhydramine) cause sedation & slow down reflexes. This prolonged reaction time is the dangerous thing. Imagine if it took you a second or two longer to take action while driving. Patients often adjust to the sedating effects without their reaction times returning to normal. They just think they have. Please use a non-sedating antihistamine like Claritin or allegra.