Why Does My Underwear Smell Like Ammonia?

If you’ve noticed an ammonia smell lingering in your underwear, it can feel confusing or even embarrassing, but the good news is that it’s usually not a serious issue. While it’s natural to feel concerned, many women experience changes in vaginal odor or unusual smells in their underwear at some point in their lives. 

Below, we’ll cover what “normal” vaginal odor smells like, why you have vaginal odor in the first place, and the most common reasons you might notice an ammonia smell. 

What does normal vaginal odor smell like?

Healthy vaginas have a natural scent, which is influenced by the delicate balance of bacteria that help keep it healthy (aka, your vaginal microbiome). Vaginal odor is a natural byproduct of your vagina’s self-cleaning process.

Healthy vaginal odor is often described as slightly musky or tangy, and it can vary from person to person. It’s important to know that having some vaginal odor is completely normal — it’s a sign of a healthy and functioning body.

The vagina maintains a balanced ecosystem of bacteria and yeast, which work together to keep it healthy and prevent infections. This process involves the production of vaginal discharge, which helps cleanse the vagina by flushing out dead cells and unwanted bacteria — so no, daily discharge is not something to worry about.

This discharge interacts with external factors like sweat, urine, and clothing, sometimes making the odor more noticeable. For example, sweat in the groin can mix with bacteria, producing a noticeable smell. Similarly, wearing tight or non-breathable clothing can trap moisture, creating an environment where odors are more likely to develop.

The way your vagina smells can also change throughout your menstrual cycle due to hormonal fluctuations. For instance, when you’re ovulating, some women notice a stronger or sweet smell because of changes in cervical mucus. After your period, you might notice a slightly metallic smell due to traces of blood. 

Certain factors — like hydration, hygiene, or medical conditions — can influence the type and strength of the smell, including the ammonia-like scent. While these changes are normal, any foul or unpleasant odor could signal an underlying issue, such as an infection or imbalance in your vaginal flora (more on that below).

Why does my underwear smell like ammonia?

An ammonia-like smell is distinct from the usual musky or tangy scent and can result from several factors. Let’s take a closer look at the most common reasons why.

Sweat and urine 

The groin is a hotspot for sweat glands (apocrine glands), and sweat contains compounds like urea, also found in urine. If sweat or a small amount of urine gets trapped in your underwear or on your skin, bacteria can break it down, creating an ammonia odor. This is especially common if you wear tight clothing, or synthetic fabrics, or delay changing out of sweaty or damp underwear after exercise.

In some cases, not wiping properly after going to the bathroom can leave traces of urine on your underwear, contributing to the odor. Proper hygiene and wearing breathable fabrics (like cotton underwear) can help reduce this issue. Make sure you wash your vulva with warm water (and unscented soap if you wish) after working out.

Dehydration

Your hydration levels have a direct impact on the smell of your urine. When you’re dehydrated, your urine becomes more concentrated with urea and other compounds, making it smell stronger. Even a small amount of concentrated urine mixed with discharge or sweat can create a noticeable ammonia-like scent.

Drinking plenty of water throughout the day not only dilutes your urine but also helps flush out toxins that can contribute to stronger smells. 

Bacterial vaginosis

An ammonia-like odor can sometimes signal a disruption in your vaginal flora, such as bacterial vaginosis (BV). Bacterial vaginosis occurs when the natural balance of good bacteria in the vagina shifts, often resulting in symptoms like a fishy smell, thin grayish discharge, and mild itching or irritation.

Although bacterial vaginosis is most commonly associated with a fishy smell, in some cases — especially when there's an overgrowth of a bacteria called Prevotella bivia — you might notice more of an ammonia-like scent. Abnormal vaginal odor caused by bacterial vaginosis also tends to smell stronger after having unprotected sex.

In rarer cases, BV infections can occur when some bacteria from the anal area make their way into the vagina. These bacteria can produce different odors, sometimes even resembling ammonia or rotten eggs. 

While bacterial vaginosis isn’t always serious, it can increase the risk of other infections if left untreated. If you suspect BV, it’s important to see a healthcare provider for diagnosis and treatment.

Urinary tract infections

Urinary tract infections (UTIs) are another potential cause of an ammonia smell. When unwanted bacteria enter the urinary tract, they can alter the composition and smell of your urine, making it stronger or unusual. Keep in mind, however, that urinary tract infections are unlikely to affect the way your discharge smells. Other symptoms of a urinary tract infection include a burning sensation when you pee, frequent urination, cloudy or dark-colored urine, and pelvic discomfort.

If you suspect a urinary tract infection, it’s essential to see a doctor for treatment, as untreated infections can lead to complications like kidney disease.

Period products

Period products like tampons, pads, or menstrual cups can sometimes trap sweat, blood, and urine, leading to an ammonia-like smell if they aren’t changed frequently enough. Using scented products can also irritate the vaginal mucosa and potentially contribute to odor.

To minimize this risk, opt for unscented products and change them every four to six hours, or more often if needed.

When to see a healthcare provider

While an ammonia-like smell is often harmless and temporary, there are times when it’s a good idea to consult a healthcare provider. If the smell persists despite good hygiene and is accompanied by unusual discharge, itching, burning, vaginal bleeding, or pain, it could indicate an infection or other underlying issue that needs attention.

Your doctor can perform tests to identify the cause and recommend appropriate treatments, whether it’s antibiotics for a UTI, medication for BV, or lifestyle adjustments.

FAQ

Why do I smell ammonia down there?

If you happen to notice an ammonia odor in your vaginal area, don’t worry — there are several reasons this could happen, and most of them aren’t serious. One common culprit could simply be sweat or urine residue. When sweat mixes with bacteria or gets trapped in your underwear, it can sometimes create an ammonia-like odor since sweat contains urea, which is also in urine. Another possibility is dehydration, which can lead to more concentrated urine that has a stronger odor, especially if any traces linger on your skin or clothes. Additionally, sometimes bacterial imbalances like BV can result in unusual odors, including an ammonia scent. Don't forget that menstrual products need to be changed regularly, and practicing good hygiene can help, too. If the smell sticks around or comes with unusual discharge, itching, or burning, it’s a good idea to touch base with a healthcare provider or take an Evvy Vaginal Health Test. 

How do I stop my underwear from smelling like ammonia? 

There are a few things you can do to stop your underwear from smelling like ammonia. Start by gently washing the vaginal area with water or a mild, unscented cleanser — steer clear of harsh soaps and douches, as they can throw off your vaginal pH. Make it a habit to change your underwear daily and opt for breathable fabrics like cotton to help reduce sweat and moisture buildup. Staying hydrated is super important, too. When you’re well-hydrated, your urine is less concentrated, which helps keep any odors at bay. So, remember to drink plenty of water throughout the day. If you tend to sweat a lot or experience urinary leakage, using panty liners and changing them frequently can help you stay dry and fresh. For menstrual hygiene, aim to change tampons, pads, or cups regularly and choose unscented products when possible. If you notice that the smell still lingers even after making these changes, it might be a good idea to chat with a healthcare provider to check for a vaginal infection like BV or a urinary tract infection.