Q for Quinn
One of the strongest fits for plastic-free kids underwear: GOTS + Ecocert certified, with truly undyed 100%-organic-cotton-body briefs for the most sensitive skin. The honest limit is the one shared across the whole kids category - the waistband uses a covered elastic strand (an OEKO-TEX poly-elastane), so even the 100%-cotton-body styles rate minimal-contact rather than plastic-free. Watch the specific style: the "Ryan" line is 100% cotton body while the "Luca" boxer is 95% cotton / 5% spandex throughout.
How clear are their specs?
States "100% organic cotton exclusive of elastic," names the poly-elastane covered elastic, lists GOTS/Ecocert certification, dye method, and country of origin per style.