What are the different forms of vaginitis and how can I tell them apart?

In general terms, vaginitis refers to inflammation of the vagina. In most cases, this inflammation is caused by infection. The two most common types of vaginitis caused by infection are bacterial vaginosis (BV) and candidal vulvovaginitis (yeast infection). 

BV and yeast infections are extremely common vaginal infections and can sometimes be tricky to tell apart. In broad terms, BV is a vaginal infection caused by bacteria, and a yeast infection is a vaginal infection caused by a fungus, also known as candida. Although they're similar in some ways, their different causes warrant different treatments. 

Since BV is caused by bacteria, its treatment requires antibiotics, like metronidazole or clindamycin. Because antibiotic use can cause yeast infections, some women find that they develop a yeast infection as a result of treating BV. When this happens, yeast treatment can be initiated during or directly after BV treatment. Luckily, the reverse does not happen–yeast infection treatment will not cause BV.

A yeast infection is caused by a fungus and therefore requires antifungal medicine to treat, like clotrimazole or miconazole. It’s important to note that treatments can come in one-day, three-day, five-day, or seven-day course options, but the seven-day treatment is almost always the most effective. The other treatment courses often cause recurrent symptoms. 

It’s worth noting that it’s possible to have both BV and a yeast infection at the same time. However, there are some classic symptoms of each infection that make them easier to tell apart. The telltale sign of BV is a fishy odor, which often becomes worse after sex. Vaginitis without a strong fishy odor is likely to be something other than BV. 

Yeast infections usually cause thick, clumpy vaginal discharge (almost like cottage cheese) and intense itching. BV can cause irritation, too, but it’s not as intense as the itching associated with yeast, while the itch from a yeast infection is hard to ignore and can be overwhelming.

When discussing BV, it’s important to understand  two behavior-driven causes. The first is douching. Although douching is marketed for cleansing, it really is not a good idea under any circumstance, as it disrupts the pH balance of the vagina. Since the vagina is loaded with good bacteria, it's important that the balance of bacteria stays more or less in its natural and healthy milieu. Douching interrupts the pH balance and can cause one type of bacteria to outgrow the other types, which can lead to bacterial vaginosis. The vagina really doesn't need any sort of special cleansing other than a mild pH-balanced soap, applied externally only.

Some women are vulnerable to developing BV when they have a new sexual partner, as it can sometimes take bodies a little bit of time to adjust to each other's bacteria. We have billions and billions of bacteria living throughout our system, and for some people, an initial BV infection is common when sleeping with someone new. For women who are particularly prone to BV in this setting, consistent condom use substantially decreases the risk of symptoms (although it's important to note that BV is not a STI).