Thrush or candida as it is otherwise known, is one of the main side effects or antibiotic or antimicrobial treatments for chronic UTI. The good news is that healthy bacteria in your gut and vagina can help to keep candida levels in check.

Why do antibiotics cause thrush?

Antibiotics can upset the gut or vaginal microbiome which may lead to the overgrowth of abnormal microbes or fungi such as bacteria or candida in the gastrointestinal tract.

Candida is an opportunistic fungus that is present in the human body normally. Probiotic bacteria that live in the gut and in other parts of the body keep the fungi from becoming a problem. Some strains of bacteria excrete anti-fungal chemicals while others provide a barrier between the gut walls and the candida spores.

Candida becomes a problem when the probiotic bacteria, the natural ‘regulators’ in the gut microbiome, are compromised.

As well as antibiotic or antimicrobial treatments these factors can make candida/thrush more likely:

  • Eating a diet high in refined carbohydrates and sugar
  • Taking oral contraceptives or using an IUD device
  • Suppression of the immune system through long-term health problems

Thrush can affect anyone, though it occurs most in babies, toddlers and older adults. Left untreated fungal infections can spread to other parts of the body.

How candida grows

The candida cells, which are relatively benign in their yeast form, adopt their fungal form and begin to grow hyphae – the long branches that grow out of the fungus. These branches invade the cells in your intestinal lining and creating inflammation.

Vaginal flora and pH levels

A healthy vaginal flora protects the body against urogenital infections. It is made up of many different types of probiotic bacteria, the predominant bacteria being lactobacilli. Indeed, these lactobacilli and candida species often co‐exist in the vagina of healthy women.

Lactobacilli protect against vaginal infection simply by colonizing the space available. They build up a barrier against candidal overgrowth by blocking the adhesion of candidal yeast cells to vaginal epithelial cells, through competition for nutrients. They also produce lactic acid and hydrogen peroxide. Lactic acid helps to maintain a healthy vaginal pH and flora. Hydrogen peroxide stops the overgrowth of ‘bad’ bacteria that cause infection. When the level of lactobacilli is disrupted and the vaginal flora becomes imbalanced, the risk of developing an infection is increased. The infections can lead to unpleasant symptoms such as itching, irritation, burning, abnormal discharge and unpleasant vaginal odour.

The balance between beneficial and harmful bacteria in the vagina is very fragile, an imbalance occurs if the vaginal pH is not acidic enough. The vagina pH should be somewhere between 3.8 and 4.5 for a healthy level of vaginal acidity. If the vagina is not acidic enough due to a shortage of lactobacilli, then fungi and ‘bad’ bacteria are able to reproduce more than they usually would.

Antibiotic treatment for a UTI can affect the vaginal flora. Two examples of infection that arise in this way are thrush (caused by overgrowth of the fungus Candida) and bacterial vaginosis (caused by overgrowth of ‘bad’ bacteria).

The role of oestrogen

Interestingly, oestrogen levels are important for the maintenance of vaginal pH. Thrush spores are noted to be at their highest during the latter half of a women’s monthly cycle when oestrogen levels are lower because the vaginal pH balance has become more alkaline. Thrush can affect women on low oestrogen birth control or when they enter peri, menopause or become post menopausal. This is again because of the loss of oestrogen.

Localised oestrogen therapy can help restore levels within the vagina and may help with the control of outbreaks of thrush.

However, too much oestrogen may encourage candida cells to multiply. A study published in the American Society of Microbiology in 2006 found, if certain types of oestradiol (a specific type of oestrogen found in birth control pills or hormone replacement therapies) are added to candida cells, this oestrogen has been shown to increase the number of germ tube and length – developments that support candida overgrowth.

Oestrogen also acts on Candida yeasts and promotes its growth, and improves its ability to cling onto vaginal epithelial cells as shown by this study published in PLoS Pathogens in 2014.

These changes together may encourage the overgrowth of Candida, and further studies are being conducted to gain a better understanding of these mechanisms.

What are the symptoms of vulval/vaginal thrush?

  • Vulval itching
  • Vulval soreness, burning or irritation
  • Pain, or discomfort, during sexual intercourse (superficial dyspareunia)
  • Pain, or discomfort, during urination (dysuria)
  • Vaginal discharge – although this is not always present. The discharge is usually odourless and can be a thin, watery fluid, or thicker, white, and a similar texture to cottage cheese.
  • Vulvovaginal inflammation
  • Erythema or redness of the vagina and vulva
  • Vaginal fissuring (cracked skin) – in severe cases

Types of candida species

Of the 150-plus species of fungal Candida, the most commons fungal species are:

  • candida albicans
  • candida krusei
  • candida glabrata
  • candida parapsilosis
  • candida tropicalis

Candida in the bladder

The use of catheters, instruments in the urinary tract either during surgery or after as well as  antibiotic therapy may also cause candida UTI. Biofilm is critical to candidal growth on devices, such as urinary catheters that are latex coated with silicone which allows the biofilm to attach and develop. This biofilm encourages fungal spores to attach and develop fungal communities.

Fungal infections can cause a lot of pain because they grow and send out tentacles that latch into the bladder wall disrupting the sensitive nerve endings within the urinary tract. Cystitis symptoms or a UTI due to an upsurge of candida may result in frequency, urgency, pain on urination and supra-pubic pain. You may often have blood in the urine as well if the vulval/vaginal skin is cracked and bleeding.

Testing for thrush

Where to get tested

GP surgeries and sexual health clinics can swab for thrush. If you’re struggling with thrush and your GP has offered no assistance then the local walk-in GUM (genito urinary medicine) clinic can help. They have staff used to treating patients discretely and confidentially with possible thrush or other vulval vaginal infections such as Bacterial vaginosis (BV) or sexually transmitted diseases/infections (STDs/STIs). They will swab and analyse under the microscope. On diagnosis, they will prescribe a suitable course of treatment.

But not all clinics will offer sensitivity testing – detailed analysis of the candida strain to identify it and any anti-fungal susceptibilities. Sadly cuts to national health budgets are limiting the services that can be offered by these clinics.  You may have to consider testing via a private clinic.

Keep on getting thrush or it doesn’t seem to go away?

If thrush persists, ask the GP for a referral to your local hospital vulval clinic. These offer specialist services dealing with issues affecting the vagina and vulva including chronic candidiasis. As well as examining you, a detailed swab will be taken and analysed in laboratory. This will determine the strain of thrush and its susceptibilities or resistances and they can prescribe the correct treatment from there.

Find a local GUM clinic near you.

Invivo – Vaginal Ecologix (available through a clinical practitioner only)

Evvy – The Evvy Vaginal Microbiome Test can ordered directly from their webpage (only available currently to US residents. They do not ship internationally).

Juno – The Juno Bio vaginal microbiome test is available globally and can be ordered from their webpage.

Systems Biology Laboratory – The Vaginal Microbiome test is available to UK mainland residents only and can be ordered from their webpage.

What to know before you get tested

Thrush is hard to culture and false-negatives are common, previous anti-fungal treatment can also affect results. Thrush spores are at their highest the week leading up to menstruation and during menses due to the alkaline changes in the vaginal tract. Menstrual blood is itself alkaline so the best time to be tested is either just before your period or shortly after it has finished.

Don’t take or use any oral or topical anti-fungal treatments 7-10 days before the test otherwise this will affect the result and you could get a false negative result.

Is it actually thrush?

The following can also cause similar symptoms to thrush and you should seek early diagnosis and appropriate treatment.

Treatments for thrush

Oral medications

Topical treatments


Eating the right diet to prevent thrush

To prevent thrush consider limiting your sugar and refined carbohydrate intake. Any change in diet must be tailored to your individual circumstances. A good starting point is to firstly look at your lifestyle and your budget and what dietary changes are possible based on these factors. We all know that a healthy diet encourages eating plenty of fruit, vegetables, healthy fats, lean protein, and other plant-based foods.

More about diet and supporting your gut health.

Lifestyle management

You may also wish to consider the following to manage candida infections on a day to day basis:

  • Switch to cotton or silk underwear from synthetic fabrics. Wearing underwear that doesn’t breathe can raise body heat and moisture in the vagina. This creates conditions for yeast spores to grow.
  • Change out of swimsuits and workout clothes as soon as possible if they are made of synthetic materials. Ideally switch to predominantly cotton based brands.
  • If possible try to wear joggers or go underwear free when at home. Tight jeans prevent air circulation and again can encourage thrush spores to multiply. You also risk chafing of already sore and inflamed vulval skin.
  • Avoid removing all pubic hair. The Royal College of Obstetricians and Gynaecologists advises that having at least some pubic hair is important as it forms a natural barrier between your skin and bacteria. Removing it by shaving actually irritates the skin – leaving the area much more prone to infections such as thrush.
  • Launder your underwear in hot water and consider adding an anti-bacterial cleaner to your laundry powder or liquid. This temperature is important as it needs to be effective in killing yeast microbes. Dry clothing using the hottest setting of the dryer, or air-dry in bright sunlight.
  • Avoid soaps, foam bath, bath salts, deodorants or talcum powder in the genital area.
  • Don’t use deodorised panty liners or vaginal douches which can upset vaginal PH and remove beneficial vaginal microbes.
  • Use a water-based lubricant during intercourse and avoid spermicidal condoms.
  • Shower after exercising and only wash your vulva with water. Always dry the vulval area and pelvic area including the creases at the top of the thighs, any moisture can encourage fungal spore growth.
  • A bicarbonate of soda bath may help soothe and relieve yeast infection symptoms and may help to regulate vaginal pH. A 2014 study published in Current Microbiology found that bicarbonate of soda killed Candida cells that lead to yeast infections. It has also been found to have general antifungal affects through a study published in 2013 in Mycopathologia.

Sanitary protection

Human blood is comparatively alkaline, with a pH of around 7.35 – 7.45. During menstruation, the presence of blood in the vagina raises the vaginal pH above normal, disrupting the usual environment, and favouring the growth of Candida. With tampons resting in the vaginal tract and no immediate outlet for the menstrual flow, for some this can alter PH levels leading to an upsurge of candida or bacterial vaginosis during or shortly after menstruation has finished. Tampons can also be drying on the vaginal tract.

Try using unscented sanitary towels as the bleach, scent and plastic in most high street and brand name sanitary towels can irritate vulval and vaginal tissue for some people. The following are recommended:


Time of the Month

Alternatively Boots and Sainsbury’s in the UK sell their own branded sanitary protection that is unscented. These products are much cheaper than Natracare or Time of the Month but they are still bleached and contain plastics. However the major irritant – the scent – has been removed.

More information

We explain how probiotics may help to repopulate the gut with healthy bacteria.

Autoimmunity and the Gut: Campbell AW. Autoimmunity and the gut. Autoimmune Dis. 2014;2014:152428.

Candida Urinary Tract Infection: Pathogenesis: John F. Fisher, Kevin Kavanagh, Jack D. Sobel, Carol A. Kauffman, Cheryl A. Newman; Candida Urinary Tract Infection: Pathogenesis, Clinical Infectious Diseases, Volume 52, Issue suppl_6, 15 May 2011, Pages S437–S451,

Chronic vulvovaginal Candida hypersensitivity: An underrecognized and undertreated disorder by allergists:  Jonathan A. Bernstein, M.D. and Luqman Seidu, M.D. Allergy Rhinol 6:e44–e49, 2015; doi: 10.2500/ar.2015.6.0113

Gastrointestinal Colonization by Candida albicans Mutant Strains in Antibiotic-Treated Mice: Stephen M. Wiesner, Robert P. Jechorek, Robb M. Garni, Catherine M. Bendel, and Carol L. Wells Stephen M. Wiesner, Robert P. Jechorek, Robb M. Garni, Catherine M. Bendel, Carol L. Wells Clin. Diagn. Lab. Immunol. Jan 2001, 8 (1) 192-195; DOI: 10.1128/CDLI.8.1.192-195.2001

Importance of Lactic Acid in Maintaining Vaginal Health: A Review of Vaginitis and Vaginosis Etiopathogenic Bases and a Proposal for a New Treatment. Haya, Javier & García, Africa & López-Manzanara, Carlos & Balawi, Maher & Haya, Lara. (2014). Open Journal of Obstetrics and Gynecology. 04. 787-799. 10.4236/ojog.2014.413109.

Vulvovaginal Candida albicans infections: pathogenesis, immunity and vaccine prospects:  Cassone, A.  BJOG 2015; 122: 785– 794.

The Vaginal Microbiota: What Have We Learned after a Decade of Molecular Characterisation? Janneke H. H. M. van de Wijgert, Hanneke Borgdorff, Rita Verhelst, Tania Crucitti, Suzanna Francis, Hans Verstraelen, Vicky Jespers PLoS ONE 9(8): e105998.

Lactobacilli Dominance and Vaginal pH: Why Is the Human Vaginal Microbiome Unique? Elizabeth A. Miller, DeAnna E. Beasley, Robert R. Dunn and Elizabeth A. Archie Front. Microbiol., 08 December 2016 DOI=10.3389/fmicb.2016.01936