The Wellness Brew - Issue 07

Personal care products are an area of daily chemical exposure that rarely gets the same scrutiny as diet or sleep — despite the fact that what goes on the body can also get into it. Many common ingredients in deodorants, shampoos, conditioners, and skincare absorb transdermally, and several have never been tested for safety at the levels of daily cumulative exposure most people actually experience. This week, we dig into the categories that carry the most meaningful daily chemical load, the ingredients worth knowing by name, and the swaps that make the most practical difference. But first, we filtered the noise — here's what's worth knowing this week.

Seven Days of Reduced Plastic Contact Cut Phthalate and Bisphenol Levels in Half

A randomized controlled trial from the University of Western Australia, published in Nature Medicine this week, tested what happens when adults minimize plastic contact across food, kitchenware, and personal care products simultaneously for seven days. The study measured phthalates and bisphenols — endocrine-disrupting chemicals found in plastic packaging, cookware coatings, and personal care products — linked to hormonal disruption, infertility, and cardiometabolic disease. The results were striking: urinary phthalate levels dropped by more than 44% and bisphenol levels dropped by more than 50% compared to a control group that made no changes. The trial was a pilot study of 60 participants, so larger replication is needed — but the impact was significant and the study design controlled, making this one of the more compelling pieces of direct evidence that reducing plastic exposure produces measurable biological change within days, not months. Harray AJ et al., Nature Medicine, April 2026

Stop Eating at Least Three Hours Before Bed

In a recent episode of The Diary of a CEO with Steven Bartlett, Dr. Rhonda Patrick discussed why meal timing relative to sleep is one of the most overlooked levers in metabolic and cardiovascular health. The underlying research supports it. A February 2026 study from Northwestern University found that stopping food intake three hours before bed and slightly extending the overnight fasting window produced measurable improvements in cardiovascular and metabolic markers in adults at elevated cardiometabolic risk. Nighttime blood pressure decreased by 3.5% and heart rate dropped by 5%, reflecting a healthier day-night rhythm. Daytime blood sugar control also improved, with participants demonstrating more effective insulin response. Critically, participants did not reduce calories — the intervention focused entirely on when they ate, not how much. Late-night eating raises core body temperature and diverts energy toward digestion at a time when the body is designed to shift into repair and recovery mode. The three-hour window gives the body time to complete digestion, allow core temperature to drop, and transition into the overnight fasting state that supports cellular repair, including autophagy. Dr. Rhonda Patrick / The Diary of a CEO with Steven Bartlett — Primary study: Grimaldi et al., Arteriosclerosis, Thrombosis, and Vascular Biology, February 2026

A Gut Bacterium That Spreads Like an Infection and Causes Memory Loss

A study published in Nature in March 2026, led by researchers at Stanford University and the Arc Institute, uncovered a striking finding in aging mice: a specific gut bacterium called Parabacteroides goldsteinii increases naturally with age, and its expansion appears to directly drive memory decline through a well-defined biological chain. The bacterium produces metabolites called medium-chain fatty acids, which trigger an inflammatory response in gut immune cells, impair the vagus nerve's ability to signal the brain, and ultimately suppress activity in the hippocampus — the region responsible for memory formation. When young mice were co-housed with older mice, their microbiomes gradually shifted to resemble those of the older animals — and their memory performance deteriorated alongside it. When researchers colonized young, healthy mice with P. goldsteinii alone, memory impairment followed. When they wiped the microbiome with antibiotics, cognitive function was restored. This is an animal study, conducted entirely in mice, and no human data exists yet — the researchers are now investigating whether P. goldsteinii plays a similar role in human cognitive aging. What makes this worth noting is that it adds to a growing body of evidence that the gut is an active regulator of brain health, not a passive bystander. One more reason to take gut health seriously. Cox TO et al., Nature, March 2026

What's Actually in Your Personal Care Products

Personal care products occupy an overlooked category of daily chemical exposure. Unlike food — which receives considerable scrutiny — what goes on the body tends to receive far less attention, despite the fact that several common ingredients absorb transdermally, entering the bloodstream through daily skin contact. The categories worth examining are those applied to large surface areas, left on rather than rinsed off, and used every single day. Frequency and surface area are the two variables that determine actual exposure load — and by both measures, personal care products used in a daily routine deserve a closer look.

Editor’s note: this is a chemical-heavy issue that can be hard to follow. Refer to the actionable takeaways section for simplified priorities. 

Why skin contact matters

Skin is not an impermeable barrier. It is a selective membrane — and for certain compounds, particularly those that are lipophilic (fat-soluble), it provides a direct route into circulation. An FDA clinical study published in JAMA found that with even a single application, six common chemical sunscreen ingredients — including oxybenzone, homosalate, avobenzone, and octinoxate — were absorbed through the skin at levels exceeding the FDA's own safety threshold for blood concentration. Some were detectable in the bloodstream weeks after last use and found in breast milk and urine. [1]

This principle extends beyond sunscreen. A 2024 study published in Environmental Health Perspectives found that recent use of lotions, ointments, and hair conditioners was independently linked to higher urinary phthalate levels in children — direct evidence that what is applied topically affects what circulates systemically. [2] Phthalates are a family of chemicals often used in personal care products to help scents last. Classified as endocrine disruptors by the Endocrine Society, phthalates are linked to metabolic disorders, infertility, neurodevelopmental delays, and hormone-sensitive cancers. [3]

The implication is straightforward: ingredients in personal care products are not simply sitting on the surface of the skin. For certain compounds, daily application is daily exposure.

Deodorant — the highest daily skin contact category

Deodorant and antiperspirant sit at the intersection of two ingredient concerns worth examining separately.

Aluminum salts are the active ingredient in antiperspirants — they work by temporarily blocking sweat ducts. Aluminum has been studied as a potential metalloestrogen, meaning it may interact with estrogen receptors in a manner that mimics estrogenic activity. The human epidemiological evidence is inconsistent — a 2024 meta-analysis of seven case-control studies found no statistically significant association between antiperspirant use and breast cancer risk. [4] While the concern over aluminum makes sense, it has yet to be established. The practical case for switching deodorants is that aluminum-free versions are widely available, functionally effective for most people, and eliminate the question entirely.

Parabens — listed on labels as methylparaben, propylparaben, butylparaben, or ethylparaben — are preservatives found in deodorants, body lotions, and leave-on products. Cell culture and animal studies have found parabens to have estrogenic activity and the capacity to promote breast cancer cell growth by interacting with cell cycle proteins. The FDA currently considers parabens safe for use in cosmetics while monitoring new data. While there is no conclusive evidence linking parabens to breast cancer, they are endocrine disrupting chemicals and therefore may interfere with hormone function. Paraben-free alternatives are widely available at equivalent price points across every category and represent a low friction swap to avoid any potential concerns.

Recommended alternatives: Primally Pure, Dr. Squatch, Native, Tom's of Maine — all aluminum-free and paraben-free, with fragrance-free options available across each brand.

Shampoo, conditioner, and hair styling products

Hair care products represent a high-frequency, high-surface-area category of exposure that receives considerably less scrutiny than skincare. Three ingredient categories are worth knowing.

Formaldehyde-releasing preservatives. Formaldehyde is classified as a known human carcinogen by both the International Agency for Research on Cancer and the U.S. National Toxicology Program. It enters personal care products not as formaldehyde itself — which would trigger obvious label concern — but through formaldehyde-releasing preservatives (FRPs): compounds that slowly emit formaldehyde over time. A 2025 study published in Environmental Science & Technology Letters found that DMDM hydantoin, the most common FRP, appeared in approximately 47% of skincare products and 58% of hair products containing FRPs. [5] These ingredients are not fringe additives — they are present in mainstream shampoos, conditioners, and styling products sold at every price point. 

On labels, look specifically for: DMDM hydantoin, diazolidinyl urea, imidazolidinyl urea, quaternium-15, and sodium hydroxymethylglycinate. The European Union requires warning labels on products containing these ingredients. In the United States, no such requirement exists.

Parabens in conditioners and styling products. The same preservative concern from deodorant applies here — conditioners in particular tend to be leave-on or slow-rinse products, increasing contact time with the scalp and skin.

Synthetic fragrance. The word "fragrance" or "parfum" on a personal care label is a legally protected proprietary designation that can represent a blend of hundreds of undisclosed chemicals. A review published in the International Journal of Environmental Research and Public Health found that over 6,000 organic chemicals are known fragrance ingredients for personal care and household products, with more than 2,000 actively used in formulations — and that the "fragrance" designation on a label may represent a complex mixture that can, individually or in combination, trigger adverse biological effects. [8] Separately, EWG laboratory testing of 17 name-brand fragranced products found an average of 14 undisclosed chemicals per product and an average of four hormone-disrupting chemicals per product — none of which were listed on product labels. [9] The practical implication is that the designation "fragrance" provides no visibility into what is actually present — and that choosing fragrance-free alternatives across deodorant, hair care, and skincare removes a substantial layer of unknown daily exposure in a single decision. 

Recommended alternatives for hair care: SEEN Haircare, Vanicream, fragrance-free options from Dr. Bronner's — all free of FRPs, parabens, and synthetic fragrance. For styling: Highland Glacial Clay Pomade, Jack Henry Hair Clay. Verify any product via EWG Skin Deep before purchasing.

Skincare — PFAS and formaldehyde in plain sight

Skincare carries two additional concerns beyond what has already been covered.

PFAS — per- and polyfluoroalkyl substances, the same family of compounds of concern in drinking water and cookware — have been identified in cosmetics at meaningful scale. A 2025 FDA report found more than 50 PFAS ingredients intentionally added to approximately 1,700 cosmetic products, appearing most commonly in eyeshadow, foundation, eyeliner, and face and neck skincare. [6] A University of Notre Dame study found PFAS in more than half of 231 cosmetic products tested — but listed on labels of only 8%. [7] The gap between prevalence and disclosure reflects that PFAS are not always added directly but may enter through ingredient processing or as contaminants.

On labels, avoid products listing any ingredient containing "fluoro" or "perfluoro" in the name. For products where label verification is difficult, EWG Skin Deep (ewg.org/skindeep) maintains a searchable database of personal care products rated for ingredient safety — a one-time audit of current products is a practical and permanent improvement.

The single highest-leverage decision across all categories

Across all personal care categories, the word 'fragrance' or 'parfum' on a label is one of the most consistent sources of undisclosed chemical exposure — appearing in deodorant, shampoo, conditioner, styling products, and skincare simultaneously. Eliminating products listing "fragrance" or "parfum" as an ingredient — in every category touched daily — removes more aggregate unknown exposure than any other individual swap. Fragrance-free does not mean unscented: it means no synthetic fragrance compounds have been added. Many fragrance-free products have a neutral or faintly natural scent from their base ingredients.

What this means in practice

Daily personal care routines are an area where a small number of ingredient-level decisions, made once, apply every single day for years. The categories covered above — deodorant, shampoo, conditioner, styling products, and skincare — are the highest-frequency, highest-surface-area points of contact in a typical routine. Swapping to cleaner alternatives in these categories does not require overhauling everything at once. The Actionable Takeaways below outline where to start.

Four things you can do this week:

1. Swap your deodorant first. Of all the personal care categories covered in this issue, deodorant represents the highest daily skin contact in a sensitive area — applied directly to the underarm, left on for hours, and used every single day. Switching to an aluminum-free, paraben-free, fragrance-free alternative is a one-time purchase that eliminates the concerns covered above in a single decision. Recommended options: Primally Pure, Native, Salt & Stone. All are widely available and functionally effective for most people.

2. Check your shampoo, conditioner, and styling products for formaldehyde-releasing preservatives. This is the most underappreciated finding in the personal care space — a known human carcinogen hiding behind ingredient names that give no indication of what they are. Before purchasing or repurchasing any hair product, scan the ingredient label for these five names: DMDM hydantoin, diazolidinyl urea, imidazolidinyl urea, quaternium-15, and sodium hydroxymethylglycinate. If any appear, replace the product. This applies to shampoos, conditioners, leave-in treatments, and styling products. Recommended alternatives: SEEN Haircare, Vanicream, Dr. Bronner's fragrance-free options, Highland Glacial Clay Pomade and Jack Henry Hair Clay for styling.

3. Audit your skincare on EWG Skin Deep. EWG Skin Deep is a free, searchable database that rates personal care products and individual ingredients for safety concerns. A one-time audit of the products currently in your routine — searching each by name — takes under thirty minutes and produces a permanent improvement to what you apply daily. When reviewing products, flag anything listing "fluoro" or "perfluoro" in the ingredient list, which indicates the presence of PFAS. For new purchases, use the database before buying rather than after.

4. Eliminate "fragrance" and "parfum" across your daily routine. Across deodorant, shampoo, conditioner, styling products, and skincare simultaneously, choosing fragrance-free formulations removes a substantial layer of undisclosed daily chemical exposure in a single category of decision. On any product label, the words "fragrance" or "parfum" represent a legally protected proprietary blend that can contain hundreds of undisclosed compounds, including potential endocrine disruptors — none of which are required to appear on the label individually. Fragrance-free does not mean unscented: it means no synthetic fragrance compounds have been added. Many fragrance-free products have a neutral or faintly natural scent from their base ingredients.

If you found this useful, please forward it to your friends and family. If you had this forwarded to you — sign up here.

Wellness, filtered.

The Wellness Brew

Sources:

Disclaimer: The Wellness Brew is for informational purposes only and does not constitute medical advice. The content published here is not intended to diagnose, treat, cure, or prevent any disease or health condition. Always consult a qualified healthcare professional before making any changes to your diet, supplement routine, or lifestyle.