If by the Dark Ages you mean the post-Roman world of the 5th century onwards then it wasn't actually that dark. Unlike pretty much every Hollywood portrayal, there weren't bands of screaming, unwashed peasants being ridden down by barbarian raiders under a perpetually overcast sky.
For anything resembling a real Dark Ages you need to look at Western Europe after the collapse of the Carolingian Empire in the first half of the 9th century, up to the unification of the German dukes under the Ottonian dynasty towards the end of the 10th. Europe was then being ravaged by Vikings, Avars and Saracens. It seems that a genuine dark age society as popularly conceived only happens in a time of perpetual raiding and warfare, which happened when the first two tiers of political authority collapsed (Emperor and kings), leaving the disunited dukes vulnerable to attack. But even then it was more a case of a village living peacefully most of the time but in fear of a future raid, rather than ongoing fire and pillage.
Oh, and the peasants knew about soap (and the sun did shine sometimes).