Nystacid contains nystatin 100,000 units, an antifungal available as an oral suspension and an ointment. The suspension treats oral thrush — white patches in the mouth — and thrush in the gut, particularly in babies. It works on contact, so it must be held in the mouth, not swallowed straight down.
What is Nystacid?
Nystacid contains nystatin, at 100,000 units per millilitre in the oral suspension and per gram in the ointment. The suspension is a Schedule 2 medicine and the ointment Schedule 1.
Nystatin is a polyene antifungal. It binds to ergosterol, a component of the fungal cell membrane that human cells do not have, and punches holes in it. The fungal cell leaks its contents and dies.
The most important thing about nystatin is that it is not absorbed from the gut. Swallowed, it passes through and out again almost entirely unchanged. That has two consequences.
It works only where it touches. Nystatin treats fungal infection on the surface it is applied to — the lining of the mouth, the gut, the skin. It cannot treat an infection anywhere else in the body, because it never gets into the bloodstream.
It is exceptionally safe. Because virtually nothing is absorbed, nystatin has almost no systemic side effects and very few interactions. That is why it is a first choice for oral thrush in newborns, where safety matters most.
The trade-off is technique: a medicine that works on contact has to be kept in contact.
What is Nystacid commonly used for?
Nystatin oral suspension is used for candida (thrush) infections of the mouth and gut:
- Oral thrush in babies — white patches on the tongue, gums and inner cheeks, sometimes with feeding fuss.
- Oral thrush in adults, particularly after inhaled steroids for asthma, after antibiotics, in denture wearers, in diabetes, and in anyone with a weakened immune system.
- Oesophageal candidiasis, causing pain or difficulty swallowing, in some cases.
- Intestinal candidiasis.
- Preventing thrush in people at high risk, including some receiving chemotherapy.
The ointment is used for candida infection of the skin — in skin folds, and for nappy rash complicated by thrush.
Oral thrush in a baby often comes with nipple thrush in the mother, and this is the most commonly missed part of treatment. The two pass back and forth during feeding, so treating only the baby leads to reinfection within days. If you are breastfeeding and your baby has thrush — especially with sore, burning or cracked nipples — both of you need treating at the same time. Ask about it specifically.
Sterilise dummies, teats and bottles during treatment for the same reason.
In adults, oral thrush has a cause worth finding. After inhaled steroids it usually means rinsing the mouth after each dose has been missed. Otherwise, recurrent oral thrush can be the first sign of undiagnosed diabetes or a weakened immune system, and is worth investigating rather than repeatedly treating.
How Nystacid fits into this medicine category
| Group | Examples | Where it works |
|---|---|---|
| Polyene antifungals | Nystatin (Nystacid) | On contact — mouth, gut, skin; not absorbed |
| Azole antifungals, topical | Clotrimazole (Fungistop Topical, Canex V), miconazole gel | Skin and vaginal fungal infection |
| Azole antifungals, oral | Fluconazole | Absorbed; treats infection throughout the body |
| Antacids and acid reducers | Pantoprazole (Praztek) | Acid, not infection |
| Antispasmodics | Hyoscine butylbromide (Hyospasmol) | Gut cramping |
For extensive or oesophageal thrush, or in someone significantly immunosuppressed, an absorbed antifungal such as fluconazole is usually needed instead. See the digestive, stomach and nausea medicines hub.
What to check before using Nystacid
Technique matters more than with almost any other medicine on this site. Because nystatin works on contact:
- Give it after feeds or meals, not before — food washes it away.
- Hold the suspension in the mouth as long as possible before swallowing, swishing it around the cheeks and gums.
- For a baby, use a clean finger or a swab to paint it directly onto the white patches, the inner cheeks, gums and tongue, rather than squirting it down the throat.
- Do not eat or drink for a while afterwards.
Shake the bottle, and use the dropper or measure supplied.
Continue for at least 48 hours after the patches have gone — usually about seven days in total. Stopping when the mouth looks clear is the commonest reason thrush returns.
Speak to a pharmacist or doctor if:
- You are breastfeeding — mother and baby usually need treating together.
- The thrush is in a newborn, or a baby who is feeding poorly or losing weight.
- There is pain or difficulty swallowing, which may mean the infection extends into the oesophagus.
- Thrush is recurrent, which warrants looking for a cause such as diabetes.
- The person has a weakened immune system, or is receiving chemotherapy.
- You use an inhaled steroid — ask about rinsing your mouth after each dose and about a spacer.
- There has been no improvement after about a week.
Possible cautions and when to ask a pharmacist or doctor
Side effects are uncommon, because so little is absorbed. Mild nausea, an unpleasant taste, or occasionally loose stools are the usual complaints. Allergic reactions are rare.
Treat both mother and baby, and sterilise dummies and teats. Reinfection is the main reason a course appears to fail.
Rinse your mouth after inhaled steroids. For an adult who keeps getting oral thrush on an asthma inhaler, this single habit — rinse and spit after every dose, and use a spacer — usually prevents recurrence entirely.
Clean dentures properly and remove them overnight, since candida colonises the fitting surface.
If it has not cleared after a full course, go back rather than starting another. Extensive or persistent thrush usually needs an absorbed antifungal such as fluconazole, and the underlying reason needs identifying.
Seek medical attention for pain or difficulty swallowing, chest pain on swallowing, a baby who is feeding poorly, unusually sleepy or losing weight, thrush that keeps returning, thrush in someone with a weakened immune system, or a rash with facial swelling or difficulty breathing.
Related medicine guides
- Browse Digestive, Stomach & Nausea Medicines guides
- Read: Hyospasmol used for
- Read: Adco Contromet used for
Frequently asked questions
What is Nystacid used for? Thrush (candida) in the mouth and gut, and on the skin as an ointment. It contains nystatin.
How do I give it to a baby? After feeds, painted directly onto the white patches, inner cheeks, gums and tongue with a clean finger or swab — not squirted down the throat.
Why must I hold it in my mouth? Nystatin is not absorbed and works only where it touches. Swallowing it straight down means it never treats the mouth.
Does my baby’s thrush mean I need treatment too? Often yes. Nipple and oral thrush pass back and forth during feeding, so both usually need treating at the same time.
How long should I use it? Usually about a week, and continue at least 48 hours after the patches clear. Stopping early is the main reason it returns.
Why do I keep getting oral thrush? Common causes are inhaled steroids without rinsing, dentures, antibiotics, and diabetes. Recurrent thrush is worth investigating rather than repeatedly treating.