text: what is yeast infection. when the vagina is itchy , what is wrong? when the vagina itches periodly, the inside part of the "lips", what causese this problem ?  thanks to all who answer vaginal yeast infections are caused by candida albicans, which, along with a few types of bacteria, are normally present in relatively small numbers in your crotch. sometimes the yeast multiply rapidly and take over, causing a full-fledged yeast infection, or, in the heart-warming terminology of the medical establishment, candidiasis or monilia. this can be due to a change in the vaginal environment, injury, sexual transmission, or hiv. common environmental disruptions that favor yeast include increased ph, increased heat and moisture, allergic reactions, elevated sugar levels, hormonal fluxes, and reductions in the populations of bacteria that are normally present.   some infections flourish in non-cotton, tight, or dirty clothes that trap heat and moisture.  your safest bet is unbleached, undyed cotton underwear and breathable clothes. it's a good idea to change your underpants regularly, like maybe once a day. if at all possible, don't sleep in underwear; if you do, put on clean stuff. yeast can live in your underwear, so be sure to wash it well, particularly during and after a yeast infection. some medical types think that when you have a yeast infection, you should wash and dry your underwear and then iron it or throw it in the microwave on high for 5 min to kill the yeast.   chemicals, such as inks, dyes, and perfumes, can upset the balance in your crotch or trigger allergic reactions that lead to yeast infections. the classic example is commercial douches, which have no benefits and are definitely harmful to the vaginal environment and your health.     condoms can promote yeast infections in two different ways. first, a lot of condoms come packaged with a lubricant that contains nonoxynol-9, a spermicide that may kill the hiv virus. several recent studies have shown that nonoxynol-9 is linked to yeast infections. if you suspect this is your problem, try using a condom that doesn't have a spermicidal lubricant, and use a different spermicide or additional barrier protection. condoms can also cause yeast infections if you are allergic to latex, although this is less common. if this is the case, don't give up hope on practicing safer sex. you may want to try some of the newer plastic (polyurethane) condoms for boys or girls.   hormones, both naturally-occurring and artificially introduced, can affect yeast. for example, pregnant women are particularly prone to yeast infections. many women taking contraceptive pills experience regular yeast infections as their hormone levels fluctuate  symptoms: feels like an intense itching, burning sensation, localized in your vagina and vulva. this itching is not always present, but can get really bad, so bad you can hardly walk, let alone ride your bike to the pharmacy or doctor to get it treated.   smells like bread or beer. in fact, it smells pretty much exactly like yeast, although the yeast used in brewing and baking is an entirely different species (saccharomyces cerevisiae). no bacteria could smell like that, so it's a great diagnostic.   monistat has a purportedly 1-day treatment called monistat-1. the active ingredient is tioconazole, a scary-powerful antifungal drug.   i hope this helps! let me know!