Does Deodorant or Antiperspirant Cause Breast Cancer?

In the late 1990s a chain email began landing in inboxes around the world. It said that antiperspirants trap toxins under the arm. Those toxins, it claimed, back up into the lymph nodes and seed breast cancer. The email named no study and no author. People forwarded it for years.

The reasoning felt sound. The underarm sits close to the breast. Antiperspirants really do block sweat. And more breast tumors are found in the upper outer part of the breast, near the armpit, than anywhere else. Line those three facts up and a story almost writes itself.

Every step in that story is either wrong or unsupported. Here is what has actually been tested.

The heart of the chain email is a claim about biology. It says sweat clears poisons, and blocking sweat traps them inside.

The American Cancer Society answers this in one line. Sweat glands in the skin, including the ones under your arms, "mainly cool the body, rather than remove toxins." Sweat is mostly water and salt. Its job is temperature control.

The organs that clear harmful substances from your blood are the kidneys and the liver. As that page puts it, most cancer-causing substances that enter the body "are removed from the blood by the kidneys and the liver and then leave the body through urine or feces."

Lymph nodes are not drains either. They are small filters packed with immune cells. Lymph fluid flows through them from the breast and arm inward, toward the chest. It does not flow outward into the skin to be sweated away. So there is no route by which a stick of antiperspirant could push toxins back into a node.

And the upper outer breast? It holds more tumors because it holds more breast tissue. Not because it is closest to the deodorant.

Antiperspirants work with aluminum salts. These form short-lived plugs in the sweat ducts, which is what stops the sweat.

Some researchers proposed that aluminum might act a little like estrogen, the hormone tied to many breast cancers. That was a fair thing to ask. It was asked, and it was measured.

Two findings came back. First, very little aluminum crosses the skin. One study of underarm use found only 0.012% was absorbed. Second, when researchers compared breast tissue containing cancer with nearby healthy tissue, aluminum levels were not meaningfully different.

In 2014 a large systematic review gathered the human safety data on aluminum exposure (Willhite and colleagues, in Critical Reviews in Toxicology). The National Cancer Institute cites it as finding no clear evidence that aluminum-based underarm products raise breast cancer risk. NCI's own summary is blunt: no scientific evidence links these products to the development of breast cancer.

Parabens are preservatives, meaning chemicals that stop mold and bacteria growing inside a product. The FDA says the ones used most in cosmetics are methylparaben, propylparaben, butylparaben, and ethylparaben.

In the 2000s, research led by Philippa Darbre reported finding parabens in samples of breast tumor tissue. That travelled fast and got squeezed down to five words: parabens in deodorant cause cancer.

Look at what the finding really was. Parabens were present in tissue. Present is not the same as guilty. The work did not show the parabens caused the tumor, and it did not show they came from deodorant. Parabens turn up in many products and in food.

NCI states it plainly: "It has been reported that parabens are found in breast tumors, but there is no evidence that they cause breast cancer."

The FDA has looked at the hormone side of it. Parabens "have significantly less estrogenic activity than the body's naturally occurring estrogen." The agency's conclusion is that parabens "have not been shown to be harmful as used in cosmetics, where they are present only in very small amounts." It adds that it does not have information showing an effect on human health, and that it keeps reading new studies.

One more thing worth knowing: most antiperspirants sold in the US no longer contain parabens at all.

Chain emails do not settle questions. Studies of actual people do. NCI lists several.

The largest is Mirick and colleagues, published in the Journal of the National Cancer Institute in 2002. Researchers interviewed 813 women who had breast cancer and 793 women who did not, asking about their underarm habits. They found no increase in risk from antiperspirant or deodorant use. They also tested the shaving version of the claim, the idea that razor nicks let chemicals in. Women who used a blade razor along with an underarm product had no increase in risk either.

A 2006 study in Iraq, by Fakri and colleagues, found no association. It was small: 54 women with cancer and 50 without.

The study most often waved around is McGrath, from 2003. It surveyed 437 breast cancer survivors and reported that the women who used underarm products more often had been diagnosed younger. That sounds alarming until you look at the design. Everyone in the study already had cancer, so there was no healthy group to compare against. And it asked women to recall decades of grooming habits after a diagnosis. NCI describes the results as inconclusive.

NCI does note that the studies as a group include conflicting results, and that more research would be needed to close every gap. That is an honest caveat. It is not a hidden warning.

Risk factors, meaning things that raise the chance of a disease, are well mapped for breast cancer. Age matters most. So do family history and inherited changes in genes such as BRCA1 and BRCA2. Hormone-related factors count too: an early first period, late menopause, having a first child later or not at all, and some forms of menopausal hormone therapy. Alcohol, extra body weight after menopause, and radiation to the chest earlier in life are also on the list.

Deodorant is not.

Nothing here says you have to use antiperspirant. Plenty of people dislike the feel, or the marks on their shirts, or simply want fewer ingredients on their skin. Those are fine reasons, and switching costs you nothing.

What is worth putting down is the fear. Time spent worrying about a deodorant is time not spent on the things that actually change outcomes: keeping to the mammogram schedule your clinician recommends, reporting a new lump or skin change quickly instead of waiting, and knowing your own family history.

And if that email lands in your inbox again, you now have a better reply than "that's a myth." You can name the studies, say how many women were in them, and say what they found.

• https://www.cancer.gov/about-cancer/causes-prevention/risk/myths/antiperspirants-fact-sheet
• https://www.cancer.org/cancer/risk-prevention/chemicals/antiperspirants-and-breast-cancer-risk.html
• https://www.fda.gov/cosmetics/cosmetic-ingredients/parabens-cosmetics
• https://www.fda.gov/cosmetics/resources-consumers-cosmetics/cosmetics-safety-qa-parabens