Change in vaginal smell after breast cancer. It happens. Let’s talk about it.

#Understand #IsThisNormal #SexAndIntimacy

In the words of medical researchers, Penn Medicine’s OncoLink, Breastcancer.org and the U.S. Office on Women’s Health. Last updated October 2026.

You noticed it. Now you can’t stop noticing it.

Maybe it’s a sourness that wasn’t there before. Maybe it’s stronger after sex, and you’ve started showering twice and wondering whether anyone else can tell. It’s one of those things that’s hard to say out loud, even to a doctor. So we’re saying it here.

Researchers who study this write that chemotherapy and hormone therapy “affect healthy vaginal microbiota in women with breast cancer.” Change the bacteria and you can change the smell. Sometimes that’s easy to fix. Sometimes it’s a reason to call your care team the same day. Here’s how the sources tell the difference, in plain English.

The short answer on vaginal smell after breast cancer

Researchers link breast cancer treatment to changes in vaginal bacteria, and one condition they connect to it, bacterial vaginosis, is known for its odor. The U.S. Office on Women’s Health says bacterial vaginosis is “easily treatable with medicine from your doctor or nurse.” A foul smell is also something to report. Penn Medicine’s OncoLink tells women taking tamoxifen to “report any bloody or foul-smelling discharge to your healthcare provider immediately.”

What the sources say, in brief

• Treatment can change your vaginal bacteria. A 2021 study of 278 women with breast cancer found “a significant decrease” in Lactobacillus, the bacteria the researchers use as the marker of a healthy vaginal balance.
• Lower estrogen plays a part. The same authors write that less estrogen “leads to depletion of lactobacilli and an increase in vaginal pH.”
• Some causes are simple to treat. Bacterial vaginosis can bring “a strong fish-like odor, especially after sex,” and is treated with medicine.
• Some changes need a call. OncoLink and Breastcancer.org both say to tell your doctor right away about blood in your discharge.

Why would breast cancer treatment change how you smell?

The short version is bacteria and estrogen. A 2021 study in the Asian Pacific Journal of Cancer Prevention looked at vaginal bacteria in 278 women with breast cancer in Kazakhstan. Most of them were receiving chemotherapy and hormone therapy, and the rest had had breast cancer two to four years earlier. The researchers found “a significant decrease in the total number of Lactobacillus spp.”

In their discussion, the authors write that chemotherapy and hormone therapy lower estrogen and progesterone, “which subsequently result in inflammatory processes of the vagina.” They name three: bacterial vaginosis, aerobic vaginitis and yeast infections (vulvovaginal candidiasis). They also write that lower estrogen “leads to depletion of lactobacilli and an increase in vaginal pH.”

The study was small and done in one country, and the authors say their findings “require further studies.” It doesn’t measure smell. What it does show is that the vaginal environment can change during and after treatment.

What does bacterial vaginosis smell like?

According to the U.S. Office on Women’s Health, “some women report a strong fish-like odor, especially after sex.” The discharge “can be white (milky) or gray.” The good news is that it’s “easily treatable with medicine from your doctor or nurse,” and a doctor or nurse can test you to confirm it. If symptoms “don’t go away within a few days after finishing the antibiotic,” the Office says to go back.

What kind of discharge is expected on tamoxifen or chemo?

Breastcancer.org says tamoxifen “commonly causes vaginal discharge that is odorless and clear or white.” OncoLink, Penn Medicine’s cancer information site, agrees: “White/clear discharge is normal.”

Chemotherapy is different. Breastcancer.org says it “can also cause yeast infections and lead to thick and whitish vaginal discharge,” and that discharge that is “thick and white or yellowish and resembling cottage cheese can be a sign of a vaginal infection.”

When should you call your doctor about a change in smell?

The sources are clear on this part.

• Foul-smelling or bloody discharge on tamoxifen. OncoLink says to “report any bloody or foul-smelling discharge to your healthcare provider immediately.” It notes “a very small risk of developing endometrial (uterine) cancer” on tamoxifen, and says women past menopause “should report any vaginal bleeding to their oncologist, primary physician or gynecologist.”
• Any blood in your discharge. Breastcancer.org: “See your doctor immediately if there is blood in your vaginal discharge.”
• A possible infection. Breastcancer.org: “Let your doctor know if you think you might have an infection.”

You don’t have to be sure something is wrong before you ask. “This smells different and I want to rule things out” is a complete sentence.

What can you do day to day?

Breastcancer.org suggests daily showers or baths “using gentle soap and warm water,” cotton underwear and loose clothing, and avoiding “scented tampons and pads, which can cause irritation.” It also says: “Don’t douche and stay away from vaginal sprays and deodorants that can irritate the vagina.”

The Office on Women’s Health explains why that one matters: “Douching removes some of the normal bacteria in your vagina that protect you from infection.” In other words, the scented-spray aisle is not your friend.

Questions to ask your care team about a change in smell

1. Could my treatment be changing my vaginal bacteria?
2. Can you test me for bacterial vaginosis, a yeast infection or another infection?
3. I’m on tamoxifen. Which changes in discharge or bleeding should I report, and to whom?
4. Which soaps, lubricants and moisturizers are OK for me to use?
5. Can you refer me to a gynecologist who works with breast cancer patients?

Quick question

Did anyone tell you your smell might change?

Yes, someone on my care team told meNo, nobody told meI found out on my own

Anonymous. We count answers, never names or emails.

More from Babette: Vaginal dryness… um, ouch. · What Helps Vaginal Dryness After Breast Cancer? · Why Does Sex Hurt After Breast Cancer?

Sources: Balmaganbetova FK, Amanzholkyzy A, Nurgaliyeva RE, Kaldybayeva AT and Zhexenova AN, Comparative Analysis of Vaginal Microbiota in Women with Breast Cancer in Kazakhstan, Asian Pacific Journal of Cancer Prevention, April 2021; OncoLink (Penn Medicine), Tamoxifen (Nolvadex®), last reviewed March 2025; Breastcancer.org, Vaginal Discharge, updated October 2023; U.S. Office on Women’s Health, Bacterial Vaginosis fact sheet. Quotations are from the sources listed. This article is general information and is not a substitute for advice from your care team.