What causes oral thrush in a 25 year old woman?
About oral candidiasis:
Hello and welcome,
Sorry you are having problems with thrush. While it is more common in babies, elderly, and immune suppressed (chemo, organ transplants, HIV), it is not that uncommon in otherwise healthy adults.
Things that can predispose an adult to oral candidiasis are antibiotics, and corticosteroid inhalers such as for asthma, and corticosteroid oral medication. Cigarettes can do this too, as can excessive amounts of alcohol or sugar consumption. Anemia can be a risk factor too.
If none of that applies to you, it would be reasonable to go to your doctor and get a CBC with differential to make sure you are not anemic, and to see if your white blood cells, in particular T-lymphocytes, are adequate. Also to get a blood sugar check.
But please do not worry that something serious is going on as oral candidiasis happens more often than you would expect and without any serious underlying pathology.
In the meantime, get adequate sleep if possible, avoid alcohol, and decrease sugar and refined carbohydrates.
I hope this information helps. Please let me know if I can provide further information or clarification.