Vaginal Thrush: How to Tell Whether That's Actually What You've Got

Most women who buy a thrush treatment are confident about what they've got, but roughly two thirds of them are wrong. Here's how to work out which group you're in before you spend the money.

A research team recruited 95 women who had already bought an over-the-counter antifungal, were carrying it, and intended to use it on themselves that day. Each of them was then examined and swabbed. Thrush was confirmed in 33.7%. Bacterial vaginosis accounted for 18.9%, mixed vaginitis for 21.1%, trichomonas for 2.1%, other diagnoses for 10.5%, and 13.7% had nothing wrong with them at all.

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Two women in three were about to treat something they didn't have. What people incorrectly think here is that those women must have been guessing, and that anyone who has had thrush before would know the difference. This reasoning was tested in the same study, and it isn't true. Women who had previously been diagnosed with thrush by a clinician were no more accurate than women who never had been, and reading the packaging made no difference either.

A 2004 review in JAMA pulled together the studies on this and looked at how much diagnostic weight each individual symptom actually carries. The conclusion was that individual signs, symptoms and clinic-based tests perform poorly enough that identifying the cause of vaginal symptoms from them is difficult. This was a review of doctors examining patients, not women assessing themselves at home.^[2]

Itching is strongly associated with thrush, and its absence makes thrush less likely. It carries no useful information about bacterial vaginosis or trichomonas, so itching is the main symptom to look out for. If there's no itch, and what you've noticed is a change in discharge or a smell, it might not be thrush you're dealing with.

The description of the discharge is less reliable than people think. Across the studies reviewed, what the patient reported about her discharge was diagnostically useful in only two of six, and the appearance of discharge on examination could not reliably separate one cause from another. The cottage cheese description does point towards thrush when it's present, but plenty of thrush produces thin discharge or barely any, and plenty of other things produce thick discharge.

Positive swabs for Candida were found in around 15% of women without any symptoms, so even a positive swab isn't automatically the answer to why you feel uncomfortable.^[3]

BV, skin conditions and Trichomonas will not improve with Canesten, and trichomonas needs an antibiotic, and if they have one, their partner needs treatment as well, otherwise it will keep coming back.

Persistent vulval itching with no discharge and no smell is more often a skin problem than an infection. Eczema and contact dermatitis of the vulva are common and can be caused by or worsened by scented washes, wipes, panty liners, and in some cases the antifungal cream itself.

Lichen sclerosus is less common. It is a long-term condition that causes itching, pale or thickened skin, and gradual changes to the shape of the vulva, and it needs a potent steroid rather than an antifungal. If you are constantly finding yourself needing treatment for thrush, it could be worthwhile to get yourself examined properly to make sure it is not Lichen sclerosus.

Don't take the above as "treating it myself is pointless". Thrush is very common, the treatments are cheap and safe, and in a first-time episode with clear itching, external soreness and no smell, it is safe to assume it could be thrush.

The way to take it is: if you take treatment and it works, that was almost certainly thrush. If it doesn't, don't assume you need more courses or a strong anti-fungal. Instead assume it could be something else entirely and write down every symptom you have before purchasing more doses.

A pH self-test is one way to narrow it down before you spend anything. In one study, 151 women read the instructions, used a vaginal pH device and interpreted it themselves, and their readings agreed closely with those taken by clinicians. Restricting anti-fungal purchases to women with symptoms and a pH of 4.5 or below cut inappropriate use by around half. These tests won't tell you that you have thrush, but they tell you when you probably don't, which is also quite useful when deciding what to do next.

Candida is not something you pick up from somewhere or someone. It is a fungus (which sounds worse than it is) normally present in the gut, the mouth and the vagina, and around 15% of women with no symptoms whatsoever would grow it on a swab if they were tested today.

Around 75% of women will have at least one episode during their reproductive years, and more than 5% get four or more in a year. If you are experiencing four or more episodes in a year it is worth booking an appointment with your GP to discuss your options as it may require a different course than can be bought over the counter.

When it becomes a problem.

Candida lives quite happily as single oval yeast cells. The trouble starts when it changes form and begins growing as hyphae, long filaments that push into the surface layer of the vaginal wall.

Those hyphae secrete candidalysin, a peptide toxin that damages the epithelial cells it's invading. The damage sets off inflammatory signalling in the epithelium, and it's that hyper-inflammatory response, rather than the fungus itself, that produces most of what you feel. This is why women can be heavily colonised and feel completely comfortable and asymptomatic. If the yeast stays in its budding form and never switches, there's nothing to react to. It explains why the misery of an episode doesn't track with how much yeast is present, because you're measuring the response rather than the actual cause.

The itch will outlast the treatment.

An anti-fungal kills the yeast within a day or so, but the inflammation it provoked doesn't switch off at the same moment. The tissue has to settle, which is why we say to allow for several days for symptoms to resolve rather than expecting overnight relief. A lot of people still take a tablet or use a pessary and on day two decide that the treatment hasn't worked, buy something else, and then credit the second purchase as what cured their symptoms when the first one was already working. 

A soothing cream is doing something.

Because symptoms are largely inflammatory, an emollient or a mild anti-inflammatory applied externally isn't just a comfort measure alongside the "real" treatment; it's treating the part of the problem you actually feel. Keep this in mind if you're weighing up your treatment options and considering a combi pack against a pessary on its own.

People looking at products may think the pessary works better than the capsule as it is being inserted closer to the source of the infection and an oral capsule will not target the thrush in the vagina as well as a pessary.

A Cochrane review pulled together 26 randomised trials covering 5,007 women and eight different antifungals to compare taking a treatment by mouth against putting one in the vagina. For clinical cure, meaning symptoms gone, there was probably little or no difference between the two at short-term follow-up across 13 trials and 1,859 women, and no difference at long-term follow-up either. In raw terms that was a 77% cure rate for intravaginal treatment against 79% for oral.^[4]

Oral antifungals did clear the yeast from the vagina better than intravaginal ones, in both the short and long term and more women had a negative swab afterwards. The same review found no matching advantage in symptoms, which is due to most of what you feel being your own epithelium reacting to the damage the fungus caused, rather than the presence of the fungus itself. Clearing the last of the yeast more thoroughly doesn't automatically make you feel better any faster.

Across 23 studies, only three women stopped treatment because of unwanted effects, which says that both routes are well tolerated. The difference is in what kind of side effects you may experience, with intravaginal treatments causing local reactions more often, meaning burning, stinging and irritation on application, while the oral route is more associated with headache.

Thrush treatments usually come in three ranges that are split into three jobs, and the packaging can make it confusing on what a medication is actually going to do for you.

An internal treatment, meaning a pessary or a vaginal cream supplied with an applicator, treats the infection itself. An external cream treats the itching and soreness on the vulva and does not treat the infection. A capsule treats the infection from the inside and does nothing directly for the external soreness.

We commonly see people buying an external cream on its own, getting a few days of relief because the inflammation is what hurts, and then finding it comes back as the cream has not actually treated anything. The other common error is the opposite, taking the capsule and being disappointed that the outside is still sore two days later.

If you have itching and soreness on the outside as well as internal symptoms, which is most people, you likely want two things rather than one, which is usually either the external cream and pessary, or external cream and oral capsule.

Vaginal creams and pessaries contain clotrimazole, these can weaken condoms and diaphragms, which means barrier contraception is unreliable during treatment and for a few days after. If you're relying on condoms, either use something else that week or take the capsule instead.

The capsules without a prescription are restricted by age, it isn't suitable in pregnancy or while breastfeeding, and shouldn't be taken for repeated episodes over a short period unless recommended by a GP.

Most people's first thought when a thrush treatment fails is to assume they need another dose, a different type of anti-fungal or that the fungus is resistant to what they tried. This list is in order of the reasons we see in the pharmacy and over emails of why treatment may have failed.

1. It wasn't thrush

If a third of women buying an antifungal have thrush, then a treatment that does nothing is quite a common outcome, and the most likely reason. Bacterial vaginosis will not respond to an antifungal. Neither will trichomonas, eczema, lichen sclerosus or an irritant reaction to a wash.

This is the thing you need to consider first, and it's the one quite a few people consider last, especially if they have experienced thrush before and are convinced they are having another episode.

2. It was thrush, plus something else

21.1% of the women had mixed vaginitis, meaning more than one thing going on at once. That's a bigger group than the ones with bacterial vaginosis alone.{{citation(1}}

Mixed infection produces a particularly confusing result: partial improvement. The itching settles because the yeast is dealt with, but the discharge or the smell doesn't, and it's easy to read that as the treatment half-working when in fact it worked completely on one of two problems.

3. It's been too early, or only the external cream has been used

Very common to see this, women take the capsules or pessary and expect instant results. Inflammation takes several days to settle after the fungus is gone. An external cream on its own was never going to clear an internal infection. A capsule on its own can cure the thrush internally but take a few more days for the external symptoms to settle rather than if both were used together.

4. It's a different species

Candida albicans causes 75 to 90% of episodes, but other species, principally C. glabrata and then C. parapsilosis, are becoming more frequent. That matters because they don't behave like albicans and don't respond like it.

Non-albicans species are intrinsically resistant to azoles, which is the drug class every over-the-counter thrush product belongs to. Around half of C. glabrata strains isolated from women with recurrent thrush show reduced sensitivity to fluconazole. So a woman whose first three episodes cleared on a single capsule and whose fourth doesn't may not have developed resistance; it might be a different organism this time.

5. Genuine azole resistance in C. albicans

It is uncommon but cases of azole resistant C. albicans are increasing. The Centers for Disease Control and Prevention in the US notes that azole resistance among vaginal C. albicans isolates is becoming more common. ^[6]

What to do next if it is a resistant or non-albicans infection

If it turns out to be resistant or non-albicans, you will need to contact your GP. Treatment for these usually involves a longer course, seven to fourteen days, using a non-fluconazole azole that cannot be bought over the counter.

Four or more episodes in a year is the point at which thrush stops being an infection you keep catching and becomes a pattern that needs more intervention than constantly buying products over-the-counter.

It isn't reinfection.

People's instinct is they got rid of it, then something lets it back in. The evidence instead points to Candida already living there before the first episode and it's usually still living there after successful treatment, because clearing symptoms and eradicating the organism are not the same thing. What varies is whether it switches into the invasive form and how hard your epithelium reacts when it does. That's why the search for a cause so often comes up empty, and why women with recurrent episodes tend to describe them as arriving without explanation.

The uncomfortable truth is that you can treat each episode as it arrives, and treatment works perfectly well on each episode yet does absolutely nothing to the pattern. You can clear thrush six times a year, successfully, and still have thrush six times a year.

What can help break out of the pattern.

The approach with the best evidence behind it is suppression: get the current episode fully under control, then keep dosing at intervals for months rather than days. However this is best done under a doctors supervision rather than taking it into your own hands.

One thing that doesn't help.

Treating a male partner gets suggested often, on the reasonable-sounding theory that you're passing it back and forth, and the trials looking at whether it reduces recurrence have not found that it does. If a partner has symptoms of their own, they should be treated for their own sake. Treating an asymptomatic partner to protect you is not a strategy with sufficient evidence behind it.

In a large share of episodes there is no identifiable trigger at all. Women with recurrent thrush frequently describe episodes that arrive without any change in medication, health, clothing or behaviour, and the search for a cause will often come up empty. The switch from harmless resident to a symptomatic infection depends heavily on how your own tissue responds; then a lot of episodes will have no external explanation.

Of course some episodes are caused by outside factors.

Antibiotics

By far the most common reason we see in pharmacy. Broad-spectrum antibiotics suppress the lactobacilli that normally keep Candida in check, which is why thrush turning up in the week after a course of antibiotics is such a familiar pattern.

Anything that raises oestrogen

Pregnancy is the clearest example, and episodes are both more common and more stubborn during it. 

Diabetes, and glucose in the urine

Poorly controlled diabetes means more sugar available in the tissue and the urine makes a better environment for yeast to grow.

SGLT2 inhibitors

This class of diabetes medicine, which includes dapagliflozin and empagliflozin, works by making you excrete glucose in your urine rather than reabsorb it. That is the point of the drug. These drugs are prescribed outside of diabetes too, such as for heart disease and chronic kidney disease.

Across the dapagliflozin trial programme, vulvovaginitis, balanitis and related genital infections occurred in 4.8% of people on dapagliflozin 10mg against 0.9% on placebo, and the difference was larger in women specifically, at 6.9% against 1.5%.

For empagliflozin the figure for female genital infection is 5.4% against 1.5% on placebo.

A UK nationwide audit found that women are at considerably greater risk than men, and that a previous genital fungal infection makes it more likely again.

That last point is the one that catches people.

Women with a history of recurrent genital yeast infections had rates of 23.1% and 25% on dapagliflozin 5mg and 10mg against 10% on placebo, so the women most affected are the ones who already had a tendency towards it.

This is not a reason to stop taking it. These are drugs with substantial benefits for the heart and kidneys, and stopping one because of thrush would be a poor trade. It's a reason to raise it with your GP as the management is different: you're not looking for a trigger to remove, you're deciding whether suppressive treatment alongside the drug makes sense.

Steroids and immunosuppression

Oral corticosteroids and medicines that suppress the immune system both increase susceptibility. Worth mentioning because inhaled steroids for asthma cause oral thrush and people reasonably wonder whether the same applies lower down. It doesn't in the same way, since that's a local effect where the inhaler deposits.

Anything that irritates the vulval skin

Scented washes, feminine hygiene products, wipes, bubble bath, and douching. The instinct to clean more thoroughly is understandable and consistently counterproductive. Plain water externally is enough.

Tight clothing and synthetic underwear.

Almost universally advised but is actually weakly supported. The evidence that changing your underwear material changes your rate of thrush is thin. It won't hurt, but it comes after everything else, if you've tried everything else and nothing improved, then consider trying it.

Sugar in the diet.

Related to but not the same as the diabetes point. In someone with normal blood glucose, cutting sugar has not been shown to prevent thrush.

Sex.

Thrush isn't sexually transmitted, but sex can provoke an episode through friction and irritation, particularly with insufficient lubrication.

Probiotics are the option we get asked about most, and the evidence is mixed.

A Cochrane review of ten randomised trials covering 1,656 women looked at probiotics used alongside conventional antifungals. They increased short-term clinical cure and mycological cure, and reduced relapse at one month, but none of that translated into better long-term cure. The review graded the evidence as low or very low quality throughout.^[7]

So: a possible short-term edge, no demonstrated long-term benefit, weak evidence, and essentially no safety concerns. If you want to try one alongside treatment, that's a reasonable thing to do with your money. It isn't a substitute for treating an episode, and it isn't the answer to recurrent thrush.