How often should you replace your underwear? A guide

We all have our favourites when it comes to underwear. The trusty ones you wear every day, the comfy pants for when it’s that time of the month and the fancier knickers for more special occasions, but have you ever considered that they may have an underwear expiration date?

While things like holes and stains may be obvious reasons for replacing your underwear there’s a host of other reasons why. To help you figure out whether it’s time to go underwear shopping, we’ve researched the signs and the potential risks to wearing old underwear. 

We’ve also offered tips for getting rid of your old undies as well as materials and products you may want to consider when shopping for new knickers - as recommended by our Mumsnet users. 

If you’re still in need of new essentials, don’t miss our guides to the best shapewear, best tights and even the best swimsuits.

In this article

How often should I replace my underwear?

“I have knickers that are at least 5 years old and socks even older. They would go in the bin if they got holes or became see through. Otherwise why would I get rid?” Mrbob 

Generally, it’s recommended that you buy new knickers every six to 12 months but that very much depends on how many pairs of knickers you own and how often you wear, wash them and what you wash them with. 

“Needing to buy new underwear every 6 -12 months is a myth. So long as you wash your knickers regularly with a mild detergent (like this one), and follow best practices regarding laundering, you can keep wearing them until they fall apart - if you want to!” explains Dr Deborah Lee from Dr Fox Online Pharmacy.

For example, if you only wear your fancier underwear every month or so, the likelihood is they are still going to be in good condition. Whereas knickers you wear for the gym or every day to work will be well worn and may need replacing more regularly. 

Read next: Find the best shapewear for women

It's essential to remember that maintaining clean and fresh underwear is important for personal hygiene and overall well being. “Without regular washing, pathogenic organisms will build up on the fabric, which can pose a health risk,” adds Dr Fox.

What are the signs that it's time to replace my underwear?

“And really there’s no need to replace undies unless it’s no longer functional/you don’t wear them. I think even my very newest pants are at least 2 years old! Many must be in their second decade!” LastToBePicked

1. They no longer fit

With regular washing and wearing, underwear may experience wear and tear, such as reduced elasticity and comfort. If you find yourself having to adjust them a lot or they’re digging in, it's time to replace your underwear.

“Wearing tight, occlusive garments encourages the growth of fungi (yeasts), causing chafing and increases the risk of local skin infections in the genital area – such as dermatitis, boils, pustules, infected hair follicles, and skin abscesses. Tight garments can also cause tingling, numbness or irritation in the upper things,” explains Dr Fox.

2. Wear and tear

You may notice stains or discolouration, especially with your white underwear which can end up looking grey. If you also notice the fabric is breaking down and you have holes, it’s a sign you need new undies.

3. Persistent odours

Do you find your knickers smell no matter how many times you wash them? “Perhaps from leaking urine or recurrent vaginal discharge such as from bacterial vaginosis (which smells like rotting fish),” explains Dr Fox. ‘It’s time to buy some new underwear.” 

Even if you’re frequently laundering, sometimes you need to give in and start again with some nice new undergarments.

4. Frequent wear/washing

If you are physically active or engage in activities that cause excessive sweating, you may want to replace your underwear more frequently.

How many pairs of underwear should I own to maintain a rotation?

To maintain a comfortable rotation of underwear, it's advisable to have at least 14 pairs of knickers. Having this number of underwear allows you to be able to wash your knickers regularly, which promotes good hygiene and prevents the build up of sweat and bacteria.

A larger rotation of underwear will also extend their lifespan by minimising wear and tear and you’ll have spares for when you are travelling and can’t wash your clothes as easily.

What materials are best for underwear to ensure comfort and durability?

The material of your knickers is one of the most important factors when picking underwear as it can affect the fit, quality, comfort and how well the knickers wash. The most common materials for underwear are:

Cotton: Soft, breathable, and hypoallergenic, it allows air to circulate, reducing the risk of moisture build-up and irritation. Look for underwear made of high-quality, combed cotton for added durability and comfort.

Modal: Modal is a type of rayon made from beech tree pulp. It is incredibly soft, lightweight, and has excellent moisture-wicking properties. Modal underwear tends to be more durable than regular cotton and maintains its shape well after multiple washes.

Microfibre: Microfibre fabrics are made of synthetic materials like polyester or nylon. They are lightweight, smooth, and wick away moisture effectively and are known to resist shrinking and fading.

Read next: Find the best tights for women

Bamboo: Bamboo-derived fabrics, like bamboo viscose, are becoming more popular for underwear. Bamboo offers natural antibacterial properties and is soft, making it a comfortable and hygienic option.

Elastane: Often blended with other materials like cotton, this adds stretch and elasticity to the underwear, improving the fit and comfort. This blend helps the underwear retain its shape and prevents sagging.

Modal-Cotton Blends: Blends of modal and cotton combine the softness of modal with the breathability of cotton, resulting in comfortable and durable underwear.

Also look at the fit, seams and shape of the underwear when choosing your new knickers.

Can I donate old underwear, or should I throw it away?

“I don’t wear bras, and buy new pants and socks when the old ones are wearing out and I can find replacements I like that aren’t expensive. When my socks and pants are worn out they go in the recycle bin.” Catsmere

While charity shops won’t take your old underwear, don’t be tempted to throw them in the bin. Local clothes recycling bins will take old undies and use the fibres to create recycled fabrics or things like insulation and packaging. Just make sure they are clean before you donate them.

How can I find the right size and fit when buying new underwear?

As many shops don’t allow you to return underwear, you’ll want to make sure you buy the right size. You can start by measuring your waist and hips and check the brand’s size chart as shops can vary in their fit.

Read next: How to wash your lingerie

Consider the style of pants. Different styles of underwear (e.g., briefs, boxers, boxer briefs, thongs) have different cuts and fits. If you can, check out the seams and waist band to make sure they’re not too tight - there’s nothing worse than elastic digging in at the waist and a seam that irritates the skin, especially around the crotch area. Check out online reviews to see what the sizing is like.

One of the most common mistakes people make when choosing new underwear is the size and fit so if you’re unsure, consider getting one pair to try before purchasing more.

Are there specific underwear styles that are better for certain activities or outfits?

From everyday briefs to more discreet undies when you’re wearing a tight dress, there are different styles that meet different needs. For everyday wear, you can't go wrong with classic styles like briefs, brazilian style or shorts. They offer good support and coverage while being suitable for most outfits.

If you workout regularly or do sports, underwear that is made from moisture wicking and stretchy materials like microfibre and nylon blends may be more suitable. For tighter outfits like skinny jeans or fitted dresses, seamless knickers or a less visible thong may be more preferable than larger pants if you want a smoother silhouette.

What is the average cost of good-quality underwear, and is it worth investing in more expensive options?

Our Mumsnet users swear by brands like M&S and John Lewis for good quality, comfortable knickers and in these shops you’re looking to pay around £5 to £12 for a single pair of knickers, but there’s also the option to buy them in multi-packs for around £14 to 16.

You may pay more for knickers at lingerie brands such as Ann Summers, Victoria’s Secret and Boux Avenue but whether you invest in more expensive options depends on your personal preferences, budget, and what you value in your underwear. If you like your underwear to look pretty or match your bras, you may choose these more premium shops. 

However, if comfort is your priority then many mid-range brands offer excellent quality without the premium price tag.

What Mumsnet users say

“Agree re. M&S Flexifit - comfortable for 'ordinary' wear and look completely innocuous. They do them in white, flesh, black and a few colours/patterns (though I prefer plain). M&S clothes are a bit crap, but their underwear is still miles better than any other 'ordinary' brand.” JennyHogon 

“I then supplement the knix with extras, mainly but not exclusively M&S Brazillians.” StarlightLady

“I’ve just jumped ship from M&S boring black cotton knickers to John Lewis boring black cotton knickers. The “Anyday” multipacks - very nice, bit more substantial than the reducing quality M&S ones.” JemimaTiggywinkle 

“Love the John Lewis 5 pack patterned cotton bikini knickers.” ursuslemonade

“I buy five new pairs of underwear from Victoria’s Secret every year. Not sure why this is a tradition but it’s one I stick to!” cliftonbear

Are there eco-friendly or sustainable underwear options available?

The most common fabric used for eco-friendly underwear is organic cotton, which is grown without the use of harmful chemicals or synthetic fertilisers. Bamboo is another highly renewable resource that grows quickly without the need for pesticides. It’s also soft, breathable and biodegradable.

You can also find great styles in tencel, modal, hemp, silk and recycled materials. Each of these fabrics is better for the environment and creates a different feel.

Can wearing old or worn-out underwear pose any health risks?

Wearing old or worn-out underwear may pose some potential health risks, though they are generally not severe. Over time, old underwear can accumulate sweat, dead skin cells, and other bodily fluids, creating a moist environment ideal for bacterial and fungal growth. This may lead to skin irritation, itching, and potentially infections like yeast infections.

If your knickers have become well worn, rough or frayed this could irritate skin, leading to chafing, redness, or rashes. If your pants are also not staying in place properly due to loss of shape, it could expose certain areas to other materials which can affect your hygiene.

Washing underwear with gentle detergent after each use will help maintain hygiene and prevent bacterial and fungal growth.

Should I replace my underwear more frequently if I engage in sports or physical activities?

While you don’t normally need to change your underwear throughout the day, if you do regular exercise or carry out strenuous activities it makes sense to change your underwear more frequently. This will help you to avoid a build up of bacteria, sweat and moisture all of which can lead to a yeast infection.

Read next: Best swimsuits, according to Mumsnet users

How we choose our recommendations 

Recommendations from real parents

With lots of busy parents on our forums, we always know this is a great place to start our research for the best products to buy right now. We have over seven million users, so we know any knickers they recommend will have been tried and tested and will cater for different sizes, shapes and budgets. 

Reviews

We also consider experts and consumers reviews, on websites like Amazon, M&S and John Lewis, when compiling our list of tips and product recommendations. This helps us work out what features are important, such as the sizing, material and seams. We always take into account both negative and positive feedback to make sure we’re recommending the best products.

Celebrated best products 

Finally, we look at products that have received awards. This, combined with real parent recommendations, reviews and expert advice, helped us recommend a variety of the best knicker for combining quality and comfort.

Why you should trust us 

We work hard to provide unbiased, independent advice you can trust. We do sometimes earn revenue through affiliate (click-to-buy) links in our articles. This helps us fund more helpful articles like this one.

About the expert

Having worked for many years in the NHS, mostly as Lead Clinician within an integrated Community Sexual Health Service, Dr Deborah Lee now works as a health and medical writer, with an emphasis on women's health, including medical content for Dr Fox pharmacy. She has published several books and remains passionate about all aspects of medicine and sexual health.

About the author

Gemma Wilcock is a freelance writer and copywriter. At Mumsnet, she creates content providing useful parenting advice, information and top products to make life easier – as a mother of two children herself, Gemma knows how important it is to get the right advice.

 After working on women’s weekly magazines for nine years, Gemma turned to freelance writing to fit around family life, writing for a range of online and print publications, charities and small businesses. She loves writing about subjects that will be helpful to the reader – and herself! - including recommending top products on Mumsnet that help parents in their day-to-day life. Whether it’s a purchase for herself or her family, she knows how important online reviews are when it comes to buying online, so she always makes sure to thoroughly research every product so we recommend the best ones on the market.