I see that particular collagen powder doesn't contain Type 11 collagen, the one most implicated in collagen induced arthritis. For me, I wouldn't risk it anyway, as labelling and health claims for collagen supplements are unregulated and don't have to be accurate or backed scientifically. Collagen sellers can and do make wild claims of benefits and never mention possible harms. Hydrolysed collagen can prompt a big immune response in some people but others don't seem to be affected.

The Scandinavian link was believed for a long time, mostly because people in countries further south didn't develop PMR, but as those countries consumed a more western diet they also had increased incidences of PMR. It is more likely that the additives in our diet, color enhancers, flavor enhancers, heat treated oils and preservatives in our food are responsible for tipping our immune systems on their heads. And of course the incidents of insecticides on the produce you buy in your supermarket doesn't help either. This is why it's very important to watch your diet when in a PMR flareup.