With wool allergies it can be the breed of sheep, the lanolin, dies, processing chemicals etc. There is no way to know for sure without doing a skin test. I think the reason people think Merino wool is safe from allergies is it tends to be less itchy than other wool. It makes it more comfortable for some people but no less chance of being allergic to it.

Back on topic:

taxdragon, why did you choose acrylic over PV for a custom kilt?