Oral thrush (or simply “thrush”) is a yeast infection caused by Candida. While uncomfortable, a thrush infection isn’t necessarily contagious. The yeast can spread from person to person, but someone who comes into contact with thrush won’t automatically develop the infection. Keep reading to learn more about oral thrush and what you can do to prevent an oral thrush infection.

A fungus called Candida is responsible for causing thrush. Candida also causes other kinds of yeast infections, such as those that occur vaginally. The fungus itself is common. In fact, you already have small amounts of it throughout your body. Such small amounts don’t cause any issues.

The fungus can turn into thrush when natural bacteria in the mouth are out of balance, however. This makes your mouth a breeding area for Candida to spread and cause infection.

Among the causes of thrush are:

  • antibiotic use
  • chemotherapy
  • dentures
  • diabetes
  • dry mouth
  • HIV
  • immune system deficiencies
  • inhaled corticosteroid use
  • smoking
  • use of steroid medications

Thrush is also common in newborns. Infants can develop the infection from exposure to yeast in the mother’s birth canal.

Thrush is most common in infants younger than 6 months, as well as older adults. However, the infection can occur in people of all ages. It’s not age itself that leads to thrush, but rather the conditions and situations that are common at certain ages.

Breastfeeding can also cause oral thrush in babies. Candida can occur anywhere on the body, including your breasts and nipples. You can’t tell the fungus is there unless there’s an infection on your skin. An infection can cause more soreness and redness than usual.

If Candida is present on your nipples during breastfeeding, the fungus then transmits to your baby. They may not necessarily get an infection from this. However, having extra yeast in their mouths increases their risk of developing thrush as a result.

On the flipside, you can get some of the fungus from your baby’s mouth on your breasts and nipples when you breastfeed. This doesn’t mean you’ll automatically develop an infection, either, though.

Symptoms of thrush include:

  • white patches inside your mouth, primarily on the tongue and cheeks
  • redness in and around the mouth
  • pain inside your mouth
  • sore throat
  • cotton-like feelings inside your mouth
  • burning sensations in the mouth
  • difficulty swallowing
  • metallic taste on your tongue
  • new sores that look like cottage cheese
  • decreased sense of taste, especially when eating and drinking
  • cracking in the corners of your mouth

Babies with thrush will also have irritation inside and around their mouths. They may also express irritability and loss of appetite. Babies who have thrush might also have a diaper rash from Candida. Learn how to tell the difference between diaper rash and yeast infection.

Thrush must be diagnosed by your doctor. They will first take a look at the physical signs inside your mouth and ask you about any other symptoms you’ve been having.

Your doctor may also take a sample from inside your mouth with a cotton swab for lab testing. This can confirm a Candida infection. The process isn’t fool-proof though, since you likely have small amounts of the yeast in your mouth with or without an infection. Your doctor will weigh the results with your signs and symptoms to make a diagnosis.

It’s important to see a doctor so they can also rule out other causes of white patches on the tongue, such as leukoplakia and scarlet fever.

In many cases, thrush goes away on its own without treatment. A persistent yeast infection may require antifungal medications. These can be taken orally or applied as ointments directly to your mouth. Antifungal rinses are another option for treating thrush.

Babies with thrush will need antifungal ointments or drops. These are applied with a sponge applicator or dropper inside the mouth and on the tongue.

More aggressive treatment measures may be required if you have immune system deficiencies. Intense treatment helps prevent thrush from infecting other areas of the body, such as the lungs, intestines, and liver.

The signs of thrush will start to diminish with time. Most people recover from thrush within 1 to 2 weeks.

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Without treatment, thrush can eventually affect the esophagus. Severe infections can spread and worsen. That’s why it’s important to call your doctor if you don’t see any improvement in your symptoms within a week. People with compromised immune systems are more vulnerable to severe infections from thrush.

Thrush may possibly be prevented with probiotics. You may also find some of the same benefits by eating yogurt with lactobacilli. Lactobacilli are bacteria that help get rid of yeast throughout the body. Talk with your pediatrician before giving any probiotics to your baby.

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Oral hygiene is also important in preventing thrush. This not only includes brushing and flossing your teeth, but also using a mouthwash to get rid of excessive microorganisms. Rinse your mouth after taking medications, too. Mouthwashes containing chlorhexidine are especially helpful if you have a weakened immune system.

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If you’re currently breastfeeding, you may also be able to prevent the spread of Candida from your body to your baby’s mouth. Because the yeast likes warm, moist environments, try to allow the area around your nipples to dry well after breastfeeding. See your doctor if you think you have the fungus on your breasts. It can cause excessive soreness and redness. You may also have deep pains within the breast area. If Candida is found on your breasts, you may need to apply antifungal ointment to the area until the yeast infection clears up.

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Thrush itself isn’t a contagious infection. You won’t necessarily “catch it” from another person. However, it’s important to take precautions if you or a loved one has thrush. Exposure to the yeast can turn into an infection, especially if your immune system isn’t working well.

Q:

Is thrush contagious through kissing?

A:

If you have an overgrowth of Candida in your mouth causing a yeast infection (thrush), that yeast can be passed from your mouth to your partner’s by kissing. However, yeast is everywhere and we all likely have small amounts in our mouths already. Candida will only cause thrush if the right conditions are present. If you think you have thrush, see your doctor as soon as you can to begin treatment. 

Karen Gill, MDAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

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