Whether it’s the cute saying on the back, the perfect color, or the fact that it doesn’t show lines under tight clothes, there are plenty of reasons you might be hanging on to your favorite pairs of underwear as long as possible—especially when you can’t find the exact same pair again.

However, difficult as it may be, there comes a time when your cherished skivvies need to make their way from your dresser drawer to your wastebasket. Wearing underwear that’s past its prime not only can be uncomfortable but can also put you at increased risk of vaginal conditions and skin concerns, among other health issues.

So, when exactly should you throw out your underwear, and what might happen if you don’t? Read on to learn the answer and hear our experts’ recommendations on the best materials, fit, and style when shopping for new underwear.

When to replace old underwear

While there is no hard-and-fast rule on when to replace underwear, it’s probably a good idea to ditch them after about a year of wear, says Anna Cabeca, DO, OBGYN, FACOG, known as “The Girlfriend Doctor” on social media, and a triple-board certified physician and a fellow of gynecology and obstetrics, integrative medicine, and anti-aging and regenerative medicine.

Although that timeframe can vary depending on the fabric and frequency of wear, there are some telltale signs your undies are past their shelf life. “You should replace your underwear if it has lost its elasticity or shape, if you notice holes, tears, and thinned-out fabric, or if there are persistent stains or odors that won’t go away after proper washing,” says Dr. Cabeca.

Beyond how your underwear looks, there’s also the hygiene factor. “Depending on the fabric and frequency of usage, some underwear can harbor bacteria and odor even after washing,” says Dr. Cabeca. “So, you should definitely rotate underwear on a moderately frequent basis.”

Can old underwear cause health concerns?

The short answer: yes. Old underwear can cause vaginal infections and skin conditions. This can happen for several reasons, but it’s mainly because the garments don’t always get 100% clean after every wash.

“As underwear ages, it can become a breeding ground for bacteria, especially if it has been worn multiple times without proper washing,” says Dr. Cabeca. “Bacteria like E. coli, which naturally reside in the genital or anal areas, can multiply and cause urinary tract infections or bacterial vaginosis if they are allowed to thrive on worn underwear.”

Keeping your undies past their expiration date can also lead to dreaded yeast infections, especially if the fabric has lost its ability to wick moisture, explains Dr. Cabeca. “Warm, damp environments are ideal for the growth of yeast, which can result in a vaginal yeast infection. This is more likely if the underwear is made of synthetic materials that trap moisture rather than breathable fabrics like cotton,” she adds.

It’s not just your vaginal and urinary tract health that can be affected—wearing old underwear can also affect your skin health, says Lindsey Zubritsky, MD, FAAD, a board-certified dermatologist and chief dermatology adviser for all free clear laundry detergent. “Over time, underwear can accumulate a buildup of odor, sweat, bacteria, and fungi that can cause an odor and lead to skin irritation in sensitive areas,” she says.

Wearing underwear that’s stretched out and lost its shape also increases the risk of skin concerns, per Dr. Cabeca. “Old underwear, particularly those with worn-out elastic bands or rough fabric, can rub against the skin, leading to irritation or small abrasions, which can make the area more susceptible to infections,” she adds.

What to look for when shopping for new underwear

Now that you know that your underwear needs to be replaced, it’s also important to understand how to buy good underwear in the first place. For ideal comfort and to prevent health issues, you need to consider material, fit, and style the next time you’re shopping for new underwear.

Fabrics

Since your undergarments constantly touch your skin, opting for breathable fabrics is a must, says Dr. Zabitsky. Both experts give cotton the thumbs up for its comfort and breathability. “[Cotton] allows for air circulation, which helps keep the genital area dry and reduces moisture buildup that can promote the growth of bacteria and yeast,” says Dr. Cabeca.

You also want to make sure any fabric you choose is moisture-wicking, meaning it’s designed to pull moisture away from the skin, per Dr. Cabeca. Microfiber, modal, or certain blends of nylon and spandex are all effective in keeping the genital area dry, especially if you’re physically active or sweat a lot, she adds. Other good fabric choices include bamboo and hemp. “These natural fibers are naturally breathable, antimicrobial, and soft, making them a good alternative to cotton,” Dr. Cabeca adds.

It’s also a good idea to avoid synthetic fabrics like pure polyester, nylon, or spandex, which can all trap heat and moisture, promoting fungal growth that can lead to yeast infections, according to Dr. Cabeca. If you are a fan of the spandex or lycra blends, which are commonly used for stretchy underwear, Dr. Cabeca suggests looking for pairs that also include moisture-wicking fabrics or a high percentage of cotton to avoid irritation.

Fit

To avoid skin chafing and irritation, you want to ensure the overall fit of your underwear is comfortable without being too loose or too tight, advises Dr. Zabitsky. Tight underwear can disrupt airflow which can lead to infections and other issues, Dr. Cabeca adds.

“While tight-fitting underwear, such as thongs or briefs, may seem flattering, they can cause chafing, irritation, and increased moisture retention in the genital area,” says Dr. Cabeca. To avoid friction and irritation, Dr. Cabeca recommends your underwear’s waistband be snug enough to stay in place but not so tight that it cuts into your skin or restricts circulation. You also want to look for underwear with flat, smooth seams as opposed to raised or bulky seams that can cause friction and lead to rashes or irritation.

Cut

The cut and style of your undies is a matter of personal preference, although both of our experts say certain cuts are usually preferable for comfort.

“Choose a style that is most comfortable for you and is appropriately fitting so that it doesn’t chafe or rub,” says Dr. Zabitsky. “Classic brief style tends to be the best tolerated in my experience.” Cuts like boyshorts or briefs that offer more coverage tend to be more comfortable than other styles like thongs or bikinis, especially if you’re prone to skin irritation or vaginal health issues, according to Dr. Cabeca.

Other things to consider

In addition to choosing the right fabric, fit, and cut, Dr. Cabeca offers these tips when shopping for new underwear:

• Look for styles with a cotton gusset (the area that covers the vaginal opening) to help further absorb moisture and keep the area day
• Avoid tags that can cause itchiness and irritation
• Choose underwear with antimicrobial or antifungal treatments, which can help reduce bacteria and yeast growth
• Limit wearing underwear that has a lot of synthetic dyes or chemical treatments

3 pairs of underwear to try

If you’re looking for new underwear that fits our experts’ criteria, check out these three selections:

• Saliryj Women’s High-Waisted Cotton Underwear (5-pack, $25) is 95 percent cotton blended with 5 percent spandex and Amazon’s best-selling newly released women’s underwear, with nearly nine out of 10 buyers giving a five-star review. Available in regular and plus sizes, the full-coverage underwear is tagless and features a double-layer waistband designed to stay in place without rolling or bunching. There’s also a breathable, double-layer crotch to help wick moisture. The budget-friendly five-packs are available in various multicolor options or all-black bundles.
• Victoria’s Secret Stretch Cotton Bikini Panties (7-pack, $40) are perfect if you’re looking for more moderate coverage than a high-waisted style. These 57 percent cotton-blend briefs offer stretchy, breathable fabric with a mid-rise waistband, high-cut leg, and seamless design. Shoppers praise them for being well-fitting, soft, and comfortable. The multi-packs of five come in a variety of colors and prints, in sizes from X-small to XX-large.
• Innersy Women’s Bamboo Underwear (3-Pack, $20) is a great option if you prefer a cotton or eco-conscious alternative. These affordable panties are made from 93 percent viscose made from bamboo for softness and breathability, along with 7 percent spandex to add stretchy comfort. The mid-rise hipster style offers moderate coverage, a skin-friendly crotch design, and thin, ¼-inch elastic bands at the leg openings for elasticity without tightness. The three-packs come in bright and classic color selections and range from size small to XX-large.

Tips on how to wash/clean underwear

Want to keep your new underwear—and the pairs still in your dresser—in their best shape and free of bacteria? Dr. Cabeca and Wendy Saladyga, fabric care expert and manager of technical performance for all free clear laundry detergent offer these tips:

• Wash underwear after every wear and in hot water, separately from other clothing if possible
• Consider washing on the delicate cycle is usually best, but refer to the care tag for the recommended setting
• Use hypoallergenic laundry detergent and avoid using fabric softeners
• Put underwear in a mesh garment bag for washing to protect them
• Try to air dry the underwear, but refer to the care tag for any special instructions
• Make sure you dry the garment thoroughly to remove all moisture