Period underwear: how it works, how long it lasts and how to care for it
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- Thinx Everyday Comfort Brief. Best for: All-day wear on its own. See options on Amazon
- Thinx Teens period underwear. Best for: Teens and first periods. See options on Amazon
- Thinx Active Mesh Bikini. Best for: Workouts and light days. See options on Amazon
How period underwear works
Thinx describes absorbent technology built into the gusset: a moisture-wicking top layer, an ultra-absorbent core layer and a leak barrier, and says the absorbent area sits mainly toward the back, varying by style. It says its underwear absorbs flow, helps control odor and wicks moisture.
You can wear it on its own or, as Thinx says, as backup protection with tampons or menstrual cups. For a reusable internal option, see our menstrual cup guide.
How long you can wear a pair
- Maker limit. Thinx says its newest styles are leakproof for up to 12 hours and to change pairs at least every 12 hours.
- Health guidance. The Office on Women's Health (OWH) says period panties can usually last about a day, depending on the style and your flow, and advises changing a product before it becomes soaked through or full.
- Follow the label. OWH says to follow the instructions that came with your period product.
For comparison, OWH notes most women change pads every few hours, and that a tampon should not be worn for more than 8 hours because of the risk of toxic shock syndrome.
OWH adds that menstrual cups and sponges may only need to be rinsed once or twice a day, and notes that on average women get a period for about 40 years of their life.
Washing and drying
| Step | Thinx care instructions |
|---|---|
| Before first wear | Wash your period underwear |
| Washing | Machine wash on cold; check whether your style needs like colors |
| Drying | Line dry, and let pairs dry completely before putting them away |
| Avoid | Ironing, bleach and dry cleaning |
| Replace | At 30 washes |
Details are from Thinx's care pages. Thinx says washing machines dilute the contents almost immediately, so your other clothes should not stain on a cold wash, and that a standard cold wash is 30C.
Materials and PFAS
Some shoppers ask whether period underwear contains PFAS chemicals. Thinx says its underwear is not made or treated with PFAS. For any brand, look for a clear statement on materials and chemical treatments before you buy.
Thinx also sells styles for specific uses, such as an Active Mesh Bikini it describes as absorbing periods, a little pee and sweat, and teen kits made from breathable cotton and designed to fit teens.
If you also have light bladder leaks, Thinx sells separate bladder leak underwear that it says holds up to 100 mL; check that a pair is designed for the kind of leak you have.
Signs of heavy bleeding
If you soak through period underwear much faster than expected, your flow may be heavy. OWH lists signs of heavy bleeding as bleeding through one or more pads or tampons every one to two hours, passing blood clots larger than the size of quarters, and bleeding that often lasts longer than eight days. It says the average woman loses about two to three tablespoons of blood during her period.
OWH says severe pain or bleeding that causes you to miss regular activities is not normal and can be treated. For cramps, see our period heating pad guide and TENS unit for period cramps guide.
When to see a doctor
OWH suggests talking to your doctor or nurse if your menstrual cycles are longer than 38 days or shorter than 24 days, or if period pain or bleeding causes you to miss school or work.
It also warns that toxic shock syndrome is a rare but sometimes deadly condition, and that if you have any symptoms you should remove a tampon, menstrual cup, sponge or diaphragm and call 911 or go to the hospital right away.
What to look for when you buy
Thinx Everyday Comfort Brief
Best for: All-day wear on its own
Thinx says its newest period styles hold up to 12 regular tampons' worth of flow, leakproof up to 12 hours.
Watch out: Change at least every 12 hours, per Thinx.
See options on AmazonThinx Teens period underwear
Best for: Teens and first periods
Thinx sells teen styles made from breathable cotton and designed to fit teens.
Watch out: Check the size chart for a close fit.
See options on AmazonThinx Active Mesh Bikini
Best for: Workouts and light days
Thinx describes it as absorbing periods, a little pee and sweat.
Watch out: Use a higher-absorbency style for heavy days.
See options on AmazonQuestions people ask
- How much does period underwear hold?
- Thinx says its newest styles hold up to 12 regular tampons' worth of flow.
- How long can I wear period underwear?
- Thinx says change at least every 12 hours; OWH says period panties can usually last about a day, depending on style and flow.
- How do I wash period underwear?
- Thinx says machine wash cold, line dry, and do not iron, bleach or dry clean.
- When should I replace period underwear?
- Thinx says to replace its period underwear at 30 washes.
- Can I wear period underwear with a tampon or cup?
- Yes; Thinx says you can wear it as backup protection with tampons or menstrual cups.
Sources
- Your menstrual cycle (womenshealth.gov), Office on Women's Health, HHS
- How Does Period Underwear Work? (thinx.com), Thinx
- How to Wash Period Underwear (thinx.com), Thinx
- FAQs and Support (thinx.com), Thinx
- Active Mesh Bikini (thinx.com), Thinx
- 3-Pair All-Day Brief Kit (Teens) (thinx.com), Thinx