Smartwool Women's Intraknit Thermal Merino Base Layer Bottom scores 50/100 on Scout's independent analysis of ingredients, additives, and lab results — a below-average score in Scout's analysis. 60% merino wool is a strong natural base, but 30% nylon and 10% elastane add two synthetic plastic fibers causing confirmed plastic leaching — a notable downgrade from Smartwool's classic merino-only legging.

Smartwool Women's Intraknit Thermal Merino Base Layer Bottom ranks #18 of 32 leggings in Scout's independent rankings. The current top score in the category is Layere Organic Cotton Capri Leggings at 95/100.

In Scout's ingredient-by-ingredient analysis, Merino Wool (60%) counts in its favor; Nylon (30%), Elastane (10%) are flagged as ingredients of concern. The full breakdown, with why each one matters, is in the Key ingredients section on this page.