PFAS in Sports Performance Undergarments, Which Brands Grade Best and Worst

Based on available materials and data, Reebok's performance underwear lineup and New Balance's core boxer brief and brief styles currently grade best among sports performance undergarments in our database, each landing at a model-based estimate of 65 out of 100 ("Good"). At the other end, a Smartwool sock line, a Feetures no-show sock, a Fruit of the Loom boxer brief, and one New Balance mesh boxer brief style all score 20 out of 100 ("Bad") in our estimates, largely tied to moisture-wicking and odor-control finishes that historically have relied on fluorinated chemistry in this product category. None of this is a lab certification of any single garment; it is a model-based estimate built from materials disclosures, brand claims, and public data, and readers who want the full picture should cross-check the PFAS Finder tool before buying.

The short version, if you're shopping for moisture-wicking underwear or performance socks and want to lean toward lower-concern options, the Reebok and New Balance products graded "Good" below are the more defensible picks based on currently reviewed data. The "Bad"-graded socks and boxer briefs from Smartwool, Feetures, Fruit of the Loom, and one New Balance mesh style deserve more scrutiny, particularly if you wear them daily against skin during high-sweat activity. For broader context on fluorinated finishes across apparel, see our clothing category roundup.

Summary comparison

Product	PFAS grade (model estimate)	Verdict
Reebok Women's Seamless Hipster	Good, 65/100	Lower concern based on reviewed materials, not confirmed PFAS-free
Reebok Men's Featherweight Performance Boxer Briefs	Good, 65/100	Lower concern, reasonable everyday pick
Reebok Men's 7 Pack Performance Boxer Briefs	Good, 65/100	Lower concern, good value multi-pack
Reebok Men's Featherweight Long Leg Boxer Briefs	Good, 65/100	Lower concern, consistent with other Reebok styles
Reebok Men's Cooling Performance Boxer Briefs	Good, 65/100	Lower concern despite added cooling finish
Reebok Men's Tech Comfort Sport Soft Boxer Briefs	Good, 65/100	Lower concern, comfort-first design
Reebok Big & Tall 6-Pack Boxer Briefs	Good, 65/100	Lower concern, extended sizing available
New Balance Men's Mesh 5" No Fly Boxer Brief	Good, 65/100	Lower concern relative to other mesh styles
New Balance Men's Premium 3" Trunk No Fly	Good, 65/100	Lower concern, premium fabric line
New Balance Men's Moisture Wicking Lightweight Boxer Briefs	Good, 65/100	Lower concern, everyday training use
New Balance Women's Athletics Brief 2.0	Good, 65/100	Lower concern among women's briefs
Reebok Women's Air Tech Performance Brief 6-Pack	Good, 65/100	Lower concern, multi-pack value
Smartwool Men's Run Cold Weather Crew Socks	Bad, 20/100	Higher concern, reconsider or verify with brand
New Balance Men's Mesh Jersey Wicking Boxer Briefs	Bad, 20/100	Higher concern despite same brand as top scorers
Feetures High Performance Ultra Light No-Show Tab	Bad, 20/100	Higher concern, popular but flagged style
Fruit of the Loom Quick Dry 360 Stretch Boxer Briefs	Bad, 20/100	Higher concern, budget line with wicking finish

How we're grading these, and why it matters

Every grade referenced in this guide is a model-based estimate built from publicly available materials lists, brand disclosures, and category patterns, not a laboratory test result on the specific garment you'd receive. A "Good" grade at 65/100 means the reviewed data shows lower relative concern compared to peers in the same category, based on available materials and data. It does not mean a product is confirmed free of PFAS, and it is not a guarantee of anything about a specific manufacturing lot. A "Bad" grade at 20/100 means the reviewed data points to higher relative concern, often tied to durable water repellent or moisture-wicking finishes that have historically used fluorinated compounds in performance textiles. If you want to check a product not listed here, run it through the PFAS Finder for an individualized estimate.

The Good graded products, in detail

Reebok performance boxer briefs and hipster line

Reebok's seven graded products here, including the Women's Seamless Hipster, the Men's Featherweight Performance Boxer Briefs, the Men's 7 Pack Performance Boxer Briefs, the Men's Featherweight Long Leg Boxer Briefs, the Men's Cooling Performance Boxer Briefs, the Men's Tech Comfort Sport Soft Boxer Briefs, and the Big & Tall 6-Pack Boxer Briefs, all share the same 65/100 estimate.

Materials, These styles are typically built from polyester-elastane or polyester-spandex blends marketed for stretch, moisture management, and four-way flexibility. Reebok's public materials disclosures for this line do not list fluorinated durable water repellent treatments as a standard finish, which is part of why the model estimate lands in the "Good" band.

Brand claims, Reebok markets these as moisture-wicking, breathable, and odor-resistant performance underwear. These are brand-stated marketing claims, not independently verified lab results, and Reebok has not published third-party PFAS test data for these specific SKUs in the sources we reviewed.

Pros, Consistent 65/100 estimate across the entire tested lineup, wide range of cuts and sizes including extended sizing, multi-pack value options, no fluorinated DWR finish flagged in reviewed disclosures.

Cons, A model estimate is not a guarantee; Reebok has not published independent lab verification specific to these garments in the sources reviewed; "Good" is a relative grade, not a certification of zero PFAS content.

New Balance's stronger performing styles

Four New Balance products also land at 65/100, including the Men's Mesh 5" No Fly Boxer Brief, the Men's Premium 3" Trunk No Fly, the Men's Moisture Wicking Lightweight Breathable Boxer Briefs, and the Women's Athletics Brief 2.0.

Materials, Nylon-spandex and polyester-spandex blends dominate this group, generally marketed around breathability and four-way stretch rather than repellency. Based on available materials and data, these styles do not carry a flagged fluorinated finish in the disclosures we reviewed.

Brand claims, New Balance describes these as moisture-wicking and breathable performance basics. As with Reebok, these are brand-stated claims rather than independently verified third-party lab findings specific to PFAS content.

Pros, Strong, consistent 65/100 estimate across four different cuts spanning men's and women's lines, well-known athletic brand with broad retail availability, no DWR-style finish flagged.

Cons, The same brand also has a lower-graded product below, showing that grade can vary meaningfully by style within one company; buyers should check each SKU individually rather than assuming a brand-wide pass.

Reebok women's brief multi-pack

The Reebok Women's Air Tech Performance Brief Panties 6-Pack rounds out the "Good" tier at 65/100.

Materials, A stretch nylon-spandex construction marketed for all-day comfort and breathability, with a mesh gusset panel.

Brand claims, Reebok positions this as a performance-ready everyday brief with air-flow technology. This is a brand marketing claim, not a verified lab statement about PFAS content.

Pros, Good value multi-pack, consistent grading with the rest of the Reebok performance line, widely available.

Cons, No published third-party verification found in reviewed sources; grade reflects category-level materials analysis, not a garment-specific lab test.

The Bad graded products, in detail

Smartwool Men's Run Cold Weather Targeted Cushion Crew Socks

This sock lands at 20/100 in our model estimate, the lowest tier covered in this guide.

Materials, A merino wool and synthetic fiber blend engineered for cold-weather cushioning and moisture control. Performance socks in this category have historically used fluorinated finishes for durability and moisture management, and the reviewed disclosures for this product did not rule that out clearly enough to lift the grade.

Brand claims, Smartwool markets this as a technical, moisture-wicking cold-weather running sock. We found no third-party lab verification in reviewed sources confirming or denying PFAS content specific to this SKU.

Pros, Well-regarded for warmth and cushioning performance, established brand in the technical sock space.

Cons, 20/100 is a meaningfully higher-concern estimate than the boxer brief and brief products in this guide; based on available materials and data, this is a product worth reconsidering or seeking direct clarification from the brand before repeat purchase.

New Balance Men's Mesh Jersey Performance Wicking No Fly Boxer Briefs

Despite sharing a brand with four "Good"-graded products above, this specific style scores 20/100.

Materials, A mesh jersey knit marketed for breathability and wicking, distinct from the fabric blends used in New Balance's higher-graded styles.

Brand claims, New Balance markets this as a lightweight, quick-drying performance boxer brief. As with the rest of this guide, that is a brand claim rather than an independently verified lab statement about fluorinated content.

Pros, Lightweight mesh construction favored by some runners for hot-weather training.

Cons, Significantly lower estimate than sibling New Balance products, illustrating that fabric technology and finish, not brand reputation alone, drives the grade. Buyers loyal to New Balance should still check the specific SKU rather than assuming brand-wide consistency.

Feetures High Performance Ultra Light No-Show Tab

This popular running sock also lands at 20/100.

Materials, A nylon-spandex blend with a targeted compression fit, marketed for ultra-light cushioning and no-show coverage.

Brand claims, Feetures promotes this as a high-performance, blister-resistant running sock. No third-party PFAS verification was found for this SKU in reviewed sources.

Pros, Widely used by runners, well-regarded for fit and durability in performance running communities.

Cons, The 20/100 estimate places it in the same higher-concern tier as the other "Bad"-graded products here; based on available materials and data, this is not a product we'd currently label lower concern.

Fruit of the Loom Men's Quick Dry & Moisture Wicking 360 Stretch Performance Boxer Briefs

Rounding out the lower-scoring group at 20/100.

Materials, A polyester-spandex stretch blend marketed for quick-dry performance at a budget price point.

Brand claims, Fruit of the Loom markets this line around moisture-wicking speed and all-day stretch comfort. These are brand-stated claims, not confirmed by independent lab testing in the sources we reviewed.

Pros, Budget-friendly, widely available at mass retailers.

Cons, Lower model-estimate grade than every Reebok and New Balance product in the "Good" tier above; buyers prioritizing lower PFAS-related concern may want to compare against the higher-graded alternatives in this guide.

What to avoid

Vague "quick dry" or "moisture wicking" marketing with no materials transparency. These claims are brand-stated, not independently verified, and the underlying finish used to achieve wicking performance is exactly where fluorinated chemistry has historically shown up in this category.
Assuming brand reputation guarantees a low-concern grade. New Balance has both a 65/100 and a 20/100 product in this same guide, which shows grade depends on the specific fabric and finish used in that SKU, not the brand name alone.
Cold-weather and cushioned performance socks with no disclosed fiber treatment. Based on reviewed data, this sub-category trends toward higher concern more than boxer briefs and briefs do, possibly tied to durability finishes applied to wool and synthetic blends.
Any product marketed as "stain resistant," "water resistant," or "odor-proof" without naming the specific finish chemistry. These functional claims are the traditional entry point for PFAS-based treatments across the broader clothing category, and undergarments are not exempt from that pattern.
Treating a single high grade as a lifetime guarantee. Manufacturing and formulation can change between production runs; a model-based estimate reflects the data available at time of review, not a permanent certification.

Our pick

Based on available materials and data, the Reebok performance boxer brief and hipster lineup and the four higher-graded New Balance styles are the more defensible choices among the sports performance undergarments we've reviewed, each carrying a model-based estimate of 65/100. Within that group, shoppers who want the broadest size range should look at the Reebok Big & Tall 6-Pack or the standard Reebok 7-Pack for value, while those wanting a lighter mesh-style fit from New Balance should reach for the Mesh 5" No Fly Boxer Brief rather than the lower-graded mesh jersey style from the same brand. None of these are labeled PFAS-free in this guide, and none should be treated as lab-confirmed; they are simply the strongest performers among the products we currently have graded data for. If a specific product you're considering isn't listed here, the PFAS Finder can generate an individualized model-based estimate, and our broader clothing roundup is a useful next stop for washing and care choices that intersect with PFAS exposure in textiles.

Frequently asked questions

Does a "Good" grade mean a product is PFAS-free?

No. A "Good" grade of 65/100 reflects a model-based estimate built from publicly available materials disclosures and category patterns, indicating lower relative concern compared to peers. It is not a laboratory certification and should not be read as confirming the complete absence of PFAS in a given garment.

Why do two products from the same brand get very different grades?

Grades are calculated at the product level based on the specific fabric blend, finish, and disclosed materials for that SKU, not the brand as a whole. New Balance's Mesh 5" No Fly Boxer Brief scores 65/100 while its Mesh Jersey Performance Wicking No Fly Boxer Briefs scores 20/100, which shows that fabric technology and treatment matter more than brand identity alone.

Is there a proven health risk from wearing a "Bad"-graded undergarment?

Research on PFAS exposure through skin contact with textiles is still developing, and any association found in broader studies is not the same as proof of causation for a specific product or individual. Based on available materials and data, a "Bad" grade signals higher relative concern warranting caution and further scrutiny, not a confirmed health outcome.