Thinx vs Knix – Scam or Legit? Exposed!

The question of which brand of period underwear is best is becoming increasingly relevant as the use of such products gains traction. Find out in our comparison of Thinx and Knix whether one is the superior choice.

Finding the finest pair of undies to wear when that bloody monster appears every month is crucial. Especially when you can’t sleep at night because you’re worried about destroying yet another pristine pair of pants.

We’ve compared two of the most well-known brands of menstrual underwear so you can find the one that works best for you.

If you’re trying to pick between Thinx and Knix, our comparison of the two brands’ advantages and disadvantages is below.

Thinx vs Knix Overview 

After years of neglect, leak-proof, useful underwear like Thinx and Knix have emerged as the norm.

Both companies pay special attention to making period underwear that won’t leak and can be worn in a variety of ways and lasts a long time.

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Thinx is becoming more mainstream as advocates for period undies spread the word throughout the world in an effort to reduce the use of environmentally damaging alternatives like tampons and pads. Thinx’s mission is to help women feel beautiful and confident throughout their periods, without the stress of worrying about leaky pads or stained clothing.

Let’s evaluate this brand by separating out its positive and negative aspects.


  • Modal cotton undergarments that are leakproof are available.
  • Includes a large size range ranging from XXS to 4XL Flow test assists you in determining the appropriate underwear for your cycle
  • Undergarments come in a wide range of shapes and cuts.
  • Absorption strength variations
  • Bundles and the bargain area can help you save money.
  • Returns are free within 60 days.
  • Excellent client service


  • Shipping is free on your first order.
  • International orders are subject to import duty.
  • It only lasts a few years.
  • There are no reusable pads available.
  • Although there is an initial investment cost, overall savings on period items are realized.


Over the past few years, Knix has made significant changes to its brand strategies and goods, elevating it to the top tier of underwear and loungewear manufacturers. Bras, underwear, leggings, shapewear, maternity clothes, and more are all available, and they’re all seamless and really comfortable (including a wide selection of period underwear).

To help you better understand this company, we will list the benefits and drawbacks of this brand:


  • High-quality undergarments and loungewear are available in a variety of sizes ranging from XS to 4XL.
  • Options for leakproof underwear and reusable pads
  • Bundles and the bargain area can help you save money.
  • Free delivery on items over $75; free 30-day returns
  • Customer service that is responsive


  • Problems with sizing charts
  • It only lasts a few years.
  • Although there is an initial investment cost, overall savings on period items are realized.

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Thinx vs Knix: Customer Reviews

After researching what people had to say about these companies online, we compiled the following lists of pros and cons.

  • Most of their period pants are excellent as a backup to other goods such as pads and tampons on lighter flow days.
  • Thinx is generally more absorbent, although most customers think Knix is only good as a backup.
  • Knix is said to be more comfy than Thinx by customers.
  • Knix is also wonderful for other comfortable loungewear and undergarments that keep you fresh all day.
  • Thinx is useful for adjusting cycle flow and comfort throughout the day while cycling.
  • Thinx offers a greater range of absorbency options than Knix.

Thinx vs Knix: PFAs

In addition, we thought you might find it useful to know about a new study that looked into the use of PFAs (per- and polyfluoroalkyl compounds) in some women’s period underwear.

PFAs, or perfluorinated alkyls, are a class of persistent, bioaccumulative, and hazardous chemicals, and are often referred to as “forever chemicals” since they do not degrade. 

Their resistance to water and stains makes them a common component in manufactured goods.

Both Thinx and Knix were sued in 2020 for utilizing PFAs in their sanitary products to wick away moisture.

Both Thinx and Knix were found to have “high amounts of fluorine,” a sign of the presence of PFAs, in a third-party analysis. Since then, Thinx has repeatedly denied using PFAs, claiming instead that their “rigorous testing for dangerous substances” applies to all of their underwear.

However, an independent lab tested Knix’s leak-proof underwear and found no trace of fluorine.

We are not able to guarantee that this is the whole truth, but we hope that by providing you with this data, you will be able to make a more educated guess about what is going on.

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Thinx vs Knix: Final Verdict

When deciding between Thinx and Knix, the brand you should choose ultimately comes down to the type of cycle you have and the level of protection you’re seeking.

Although Knix reads better on paper, our experience has been that Thinx performs better in practice (and so have many other customers). Even though Knix are less expensive, Thinx are worth the additional investment because of their higher quality and greater capacity.

While Knix claims that some of their pairs can hold as much blood as eight tampons, numerous customers have complained that this is not the case. However, Thinx’s projections appear to be more accurate.

Those who experience a particularly heavy flow may wish to err on the side of caution and try out some period undies first. In other cases, not even the most absorbent alternatives will suffice.

Since they’re so comparable, take advantage of the no-hassle return policies to choose your preferred brand.

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