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Vaginal thrush is common infection, easily treated with OTC medication, but it can be confused with a number of other conditions and several warning symptoms require referral, as Alan Nathan explains

WHAT’S THE CAUSE?

Vaginal thrush (vulvovaginal candidiasis) is caused by a yeast – Candida albicans – a usually harmless inhabitant of the gastrointestinal tract, skin and vagina, which overgrows to cause infections when conditions allow. Predisposing factors include: pregnancy; diabetes; broad-spectrum antibiotics; immunocompromised status; immunosuppressant drugs, including oral steroids; bath additives; vaginal deodorants; and preparations for vulval pruritus containing local anaesthetics; wearing occlusive underwear.

HOW COMMON IS IT?

• Three-quarters of women are thought to suffer an attack at least once in their life, with 40–50 per cent having more than one episode. Peak incidence is between 20 and 40 years of age.

SIGNS AND SYMPTOMS

• Irritation or itching in the vulvovaginal area, often intense and burning.
• Vaginal discharge, either creamy- coloured, thick and curdy in appearance or thin and rather watery, but with no offensive odour.
• There may be stinging on passing water due to inflammation of the vulva, but otherwise no pain and no increased frequency or urgency of micturition.
• The vulva may be reddened and swollen, and external skin may be excoriated and raw from scratching.

WHAT ELSE COULD IT BE?

• Bacterial vaginosis: vaginitis (vaginal inflammation) caused by a combination of bacterial species usually present at low counts in the vagina. When these are present at higher levels, they disrupt the normal flora and cause infection. Discharge may be confused with thrush, but it is white and watery with a strong ‘fishy’ odour. Itching is a less prominent feature than in candidiasis.
• Trichomoniasis: a sexually-transmitted disease caused by a protozoan parasite, Trichomonas vaginalis. As in thrush, there is vulval itching, but discharge is profuse, frothy, yellow-green in colour and with an unpleasant odour.
• Cystitis: with thrush, discomfort when urinating may be confused with dysuria associated with cystitis. However, in thrush the discomfort and burning are in the external vaginal area rather than in the bladder and urethra, as in cystitis.
• Atrophic vaginitis: in postmenopausal women lack of oestrogen reduces vaginal resistance to infection and injury, which can produce similar burning and itching symptoms to thrush, but thrush is uncommon in postmenstrual women.
• Adverse drug reactions: drugs that can predispose to thrush include broad-spectrum antibiotics, corticosteroids and drugs that can affect oestrogen levels, including oral contraceptives, HRT, tamoxifen and raloxifene.

RED FLAGS – WHEN TO REFER

• If vaginal candidiasis has not been previously diagnosed by a doctor (a previous medical diagnosis is a licensing condition for OTC sales). Other vaginal infections, some serious and all requiring treatment with POMs, have features that could be confused with thrush.
• Patients with recurrent attacks: more than two in the previous six months may indicate an underlying cause, such as diabetes.
• Patients under 16 or over 60 years of age: thrush is rare in these age groups due to the lack of vaginal oestrogen, which favours growth of C albicans, but lack of oestrogen increases susceptibility to other vaginal infections. OTC treatments are not licensed for use in these groups.
• Pregnant or breastfeeding women:
  OTC treatments are not licensed for use in these groups.
• Abnormal or irregular vaginal bleeding.
• Any blood in vaginal discharge.
• Vulval or vaginal sores, ulcers or blisters.
• Lower abdominal pain or dysuria, which may indicate a urinary tract infection.
• Patients with a previous history of sexually transmitted disease or exposure to a partner with such a history, as other infections may be present.
• No improvement after treatment with OTC medication.

OTC TREATMENTS

• Fluconazole Presented as a single-dose 150mg oral capsule. Well-absorbed when taken by mouth, symptoms usually improve 12–24 hours after administration. Adverse effects are generally mild and mainly gastrointestinal, including abdominal pain, diarrhoea, nausea and vomiting and flatulence. Fluconazole interacts with a number of drugs, including those metabolised by cytochrome P450 enzymes, but interactions are unlikely to be clinically significant with a single dose of fluconazole.
• Clotrimazole Only used topically due to adverse effects when given orally and varying absorption rates, and because it is metabolised in the liver to inactive compounds. Available for intravaginal use as a single 500mg pessary, a 5g prefilled single application of 10 per cent cream, and 2 per cent cream for twice or three times daily application to the external genitalia. Symptoms usually begin to improve more quickly than with oral fluconazole.

PRESCRIPTION TREATMENTS

Oral itraconazole; intravaginal presentations of miconazole, econazole and fenticonazole; ketoconazole cream for external use.

ADDITIONAL ADVICE

• Sexual intercourse should be avoided until cure is complete, to avoid transfer of infection and reinfection.
• Candida infection can be transferred from the bowel; after bowel movements the anus should be wiped from front to back to help prevent transfer of organisms.
• Women susceptible to attacks should:
 - Keep the vulva cool and dry with careful hygiene, use of cotton rather than synthetic underwear, and drying carefully after washing the vaginal area, as the infection thrives in a moist, warm environment
 - Avoid use of foam baths, douches and vaginal deodorants, which can strip away the protective lining of the vagina.