Nystatin is an antifungal medication used to treat yeast infections caused by Candida, particularly in the mouth, throat, intestines, and on the skin. It has been a staple treatment for these infections since the 1950s and remains widely available in several forms, including oral suspensions, tablets, creams, and powders.
How Nystatin Works
Nystatin belongs to a class of antifungals called polyene macrolides. It works by binding to a specific component in fungal cell membranes called ergosterol, which human cells don’t rely on. When nystatin latches onto ergosterol, it punches small holes (channels) in the fungal cell wall. Ions and other essential contents leak out through those channels, and the fungal cell dies.
One important feature of nystatin is that it is barely absorbed into the bloodstream. When you swallow it or apply it to skin, it stays local, acting directly on the yeast at the site of infection. This makes it effective for surface-level fungal infections but unsuitable for treating fungal infections that have spread deeper into the body.
Oral Thrush
The most common use of nystatin is treating oral thrush, a yeast infection that causes white patches on the tongue, inner cheeks, and sometimes the roof of the mouth or throat. Thrush is especially common in infants, older adults, people wearing dentures, and anyone with a weakened immune system. It also frequently develops after a course of antibiotics, which can disrupt the natural balance of microorganisms in the mouth.
For thrush, nystatin comes as an oral suspension (a liquid you swish around the mouth before swallowing). The standard technique is to place half the dose on each side of the mouth, swish it around to coat all the affected areas, and then swallow. For infants and young children, a dropper is used to apply the liquid directly to each side of the mouth, and feeding should be avoided for 5 to 10 minutes afterward so the medication has time to work on the tissue.
Treatment typically continues for at least 48 hours after visible symptoms clear up, and courses commonly run 7 to 14 days. It’s important to finish the full course even if the white patches disappear early, because stopping too soon can allow the infection to return.
Efficacy Compared to Other Options
Nystatin works for many people with mild thrush, but its cure rates are not as high as newer systemic antifungals. Clinical studies have reported cure rates as low as 54 percent with nystatin oral suspension. In one study of infants, only about 29 percent receiving nystatin were clinically cured after 10 days, compared with 100 percent of infants treated with fluconazole for seven days. The microbiologic cure rate (completely eliminating the yeast on culture) was even more stark: roughly 6 percent for nystatin versus 73 percent for fluconazole.
This doesn’t mean nystatin is a poor choice in every situation. It remains a reasonable first-line option for mild, uncomplicated thrush, particularly because it stays local and has very few side effects. For more stubborn or recurrent infections, or in immunocompromised patients, a healthcare provider will often move to a systemic antifungal instead.
Intestinal Yeast Infections
Nystatin tablets are used to treat fungal infections of the stomach lining and intestines. Because the medication passes through the digestive tract without being absorbed into the bloodstream, it contacts yeast directly along the gut wall. This makes it useful for intestinal candidiasis, a condition that can cause bloating, diarrhea, and abdominal discomfort. Intestinal yeast overgrowth sometimes develops alongside oral thrush, so both areas may be treated simultaneously.
Skin and Diaper Rash
Topical nystatin, available as a cream, ointment, or powder, treats Candida infections on the skin. The most familiar example is yeast-related diaper rash in babies, which looks different from ordinary irritation: it tends to be bright red with well-defined borders and small satellite spots around the edges. Nystatin cream applied to the affected area several times a day usually clears this type of rash within one to two weeks.
Adults can develop similar yeast skin infections in warm, moist areas of the body, including skin folds under the breasts, in the groin, or between fingers. Nystatin powder is sometimes preferred in these areas because it helps keep the skin dry while treating the infection. The topical forms are applied directly to clean, dry skin and are generally used for 14 days or until a few days after symptoms resolve.
Who Should Not Use Nystatin
Nystatin is considered one of the safest antifungal medications available, largely because so little of it enters the bloodstream. It has been used in premature newborns, pregnant women, and elderly patients with relatively few concerns. The main contraindication is a known allergy to nystatin itself, which is rare.
Side effects are mild when they occur. The oral suspension can cause mouth irritation, nausea, or diarrhea. Topical forms occasionally cause skin irritation or a mild rash at the application site. Serious reactions are extremely uncommon.
What Nystatin Does Not Treat
Because nystatin is not absorbed into the bloodstream, it cannot treat systemic fungal infections, meaning infections that have entered the blood or spread to internal organs. It also does not work against bacterial or viral infections, nail fungus, or fungal infections caused by organisms other than Candida. If you have a vaginal yeast infection, nystatin vaginal tablets exist but are less commonly prescribed today than other topical or oral antifungals that tend to work faster.
Nystatin is also ineffective against Candida species that have developed resistance, though resistance to nystatin remains relatively uncommon compared to resistance patterns seen with some other antifungal classes. If an infection is not improving after a full course, the yeast may need to be cultured to confirm the species and check its sensitivity to different medications.