If your doctor has ruled out any infections, the likely answer is that the discharge is normal for you.

Almost all women, especially during childbearing years, have some vaginal discharge at some point for no obvious reason. For some it's an ongoing problem. If this is the case then scrupulous personal hygiene, with a shower or bath at least once a day, regular change of cotton underwear and the use of panty liners help most women to cope.

When the discharge is yellow and foul it's important to check for infection, but even this can be normal. However, there are other possible causes.

Infections

Infections are commonly caused by:

• Candida, a fungal yeast that usually causes thick, white discharge
• Trichomonas vaginalis, a protozoan parasite
• Bacterial infection, such as chlamydia or gonorrhoea

Signs that discharge may be caused by infection include a change in colour, an unpleasant smell and itching.

Infections are easily treated. For example, you can buy treatments for candida directly from the pharmacist (although you will need to see a doctor if you think it is a bacterial infection, which needs a prescription for antibiotics).

There's also a condition called non-specific vaginitis. This occurs when the bacteria that normally inhabit the vagina multiply and cause an unpleasant fishy-smelling discharge.

The cause of this isn't clear, but it may be related to stress or being run down. Ensure you follow the usual advice to keep your immune system healthy with a balanced diet and plenty of rest.

Foreign bodies

Occasionally, discharge is caused by a forgotten tampon, diaphragm or retained pessary. I'm sure your doctor will have checked for this.

Allergy

Inflammation of the vagina may be caused by an allergy, and this can result in a discharge. Common allergens include:

• Spermicidal creams in barrier contraceptives
• Chemicals in soaps, vaginal douches or shower and bath products

You may want to try changing the bath or shower products that you use, to see if this helps you.

Further help

A great place for an expert opinion on problems like this is your local genitourinary medicine (GUM) clinic. The staff can advise you on a range of problems - basically anything to do with the genitals or urinary system.

Your local GUM clinic will be listed in the telephone directory, or ask at your GP's surgery or library. You probably won't need an appointment, but you may have to wait to be seen.

This article was last medically reviewed by Dr Trisha Macnair in September 2008