While vaginas all smell slightly different, the scent is usually mild and natural. A strong and unpleasant smell, such as an onion smell, can signify infection or another health problem.

The body naturally produces a discharge that keeps the vagina healthy and free of harmful bacteria and irritants. However, it is vital that people take care to clean the area surrounding the opening to the vagina, known as the vulva.

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A strong smell of onions is unlikely to be natural but could occur due to sweat, poor hygiene, specific foods in the diet, or infection.

We look at the possible causes in more detail and explain how to treat this symptom.

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Seven possible causes

Possible causes of a vagina that smells like onions include:

1. Food

Eating food with a strong smell can affect body odor. Onions, garlic, spices, and vinegar are among the foods that can change the smell of sweat.

Sweat can combine with vaginal discharge to make the vagina smell of strong foods, such as onions or garlic.

A person would generally have to eat more onion than usual for it to affect their body odor.

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2. Forgotten tampon

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A forgotten tampon may cause an unpleasant odor.

If someone forgets to remove a tampon, it can cause an unpleasant odor. The smell can occur with or without discharge.

If there is discharge, it may be an unusual color such as pink, grey, brown, green, or yellow.

Other symptoms may include fever, pain between the belly button and genitals, pain when urinating or having sex, or itching and redness around the vulva.

It is essential to remove the tampon as soon as possible. If the individual cannot find or remove the tampon, they should see a doctor.

If a tampon remains in the body for too long, there is a risk of toxic shock syndrome (TSS). Symptoms of TSS include:

TSS can be an emergency. Anyone with these symptoms who suspects they may have TSS should seek immediate medical attention.

3. Hygiene

The vagina keeps itself clean naturally by producing a discharge. However, a person should regularly wash the vulva with warm water to remove any discharge and keep the area free of harmful bacteria.

The vulva is close to the urethra and rectum, so cleaning properly after urinating or passing stool is also important.

Urine sometimes has a strong odor, which people may confuse with a vaginal odor, especially if there is undetected urine leakage.

The natural balance of bacteria in the vagina keeps it healthy, but if an imbalance occurs, it can cause problems.

Simple hygiene tips can help to maintain the optimal balance of vaginal bacteria and reduce the chances of an unpleasant smell developing. These tips include:

  • wearing clean underwear every day
  • choosing underwear made of a breathable, natural fabric, such as cotton
  • using a mild soap and warm water to wash the vulva
  • avoiding the use of douches or perfumed products
  • showering regularly, particularly after exercise

4. Hormonal changes

Hormone levels in the body change throughout the menstrual cycle, as well as during pregnancy, perimenopause, and menopause. These hormonal changes can affect the way the vagina smells.

Vaginal odor usually becomes more noticeable when there is an increased level of the hormone estrogen in the body. This will occur when a person uses certain hormonal contraceptives as well as during ovulation and pregnancy.

The amount, texture, and scent of vaginal discharge can also vary over time. Vaginal discharge will not usually have a strong or foul smell. If it does, this may be a sign of infection.

5. Bacterial vaginosis

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An unpleasant smell may be a symptom of bacterial vaginosis.

Bacterial vaginosis (BV) is an infection resulting from an imbalance in the bacteria in the vagina. According to the Centers for Disease Control and Prevention (CDC), it is the most common infection of the vagina for women aged 15–44.

One of the symptoms of BV is an unpleasant smell. Other symptoms may include:

  • watery discharge that is white or gray
  • pain
  • burning

People who are sexually active and those who use douches are more at risk of getting the infection, which will require treatment with antibiotics.

A doctor should be able to suggest ways to prevent reinfection in the future.

6. Trichomoniasis

Trichomoniasis is a sexually transmitted infection (STI) that can cause an unpleasant-smelling discharge. The discharge may be yellow or green, and the vulva may feel irritated.

Doctors will treat the infection with medication and will often recommend abstaining from sexual activity until the infection clears. All sexual partners should also seek treatment so that the infection does not continue to pass back and forth.

7. Yeast infection

Yeast occurs naturally in the vagina and helps to keep it healthy. However, it can multiply above normal levels and cause a yeast infection.

A yeast infection can result in thick, white discharge. Although this often does not smell, in some cases it may have an unpleasant odor.

Other symptoms include itching, burning, and redness around the vulva. It is possible to treat the infection using antifungal medication.

Diagnosis and treatment

A doctor should be able to diagnose the cause of a vagina smelling like onions. They will ask about any additional symptoms that have occurred.

If a bacterial infection is responsible for the smell, the doctor may prescribe antibiotics. However, if a person has frequent or recurrent infections, a preventative medication may be necessary.

If the vagina smells mildly of onions, keeping a food diary can help to determine whether or not diet is the cause. Removing strong-smelling foods from the diet may change the body’s scent.

Introducing better hygiene habits can also have an impact. Showering more regularly, switching to cotton underwear, and avoiding the use of scented or irritating products can all help to reduce any unpleasant odors.

Prevention

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Regular exercise is recommended for good overall health.

A healthful diet and regular exercise are essential for good overall health, including maintaining a healthy vagina.

Pelvic floor exercises can help to strengthen the muscles that support the vagina. This could be particularly beneficial for anyone experiencing any issues relating to this area, such as frequent urine leakage.

Using a mild soap when showering and avoiding perfumed products are good hygiene practices that can help prevent a bacterial infection.

Wearing cotton underwear helps to keep the vulva clean and dry. People can find cotton underwear in clothing stores or online.

Practicing safe sex by using barrier protection, such as condoms, can help prevent an STI. It is also essential to have regular checks for STIs.

When to see a doctor

It is normal to have slight changes in the smell of the vagina, or in the color and texture of vaginal discharge.

However, the smell can become strong or unpleasant. If this occurs and the smell does not go away after showering and changing clothes, it may be due to infection.

The symptoms of an infection can include unusual discharge, fever, pain, and itching. Medications are an effective treatment for many infections, and prompt treatment can help to prevent complications.