Costco is genuinely great for a lot of things. But not everything on those warehouse shelves deserves a spot in your cart, especially if you’re trying to reduce your family’s daily chemical exposure.

Some of the most problematic items aren’t obscure. They’re popular, inexpensive, and easy to grab in bulk without a second thought. That’s exactly what makes them worth talking about.

Here are three categories I avoid at Costco, why they concern me, and what I choose instead.

Why Common Products Are Worth a Second Look

Many everyday products contain chemical additives, synthetic materials, or ingredients that have raised flags among researchers and environmental health advocates. The concern is the cumulative effect of using dozens of these products repeatedly, every day, over the years.

1. Plastic Flip-Flops

Flip-flops are a summer staple, and Costco carries them in bulk at unbeatable prices. But most cheap plastic sandals are made from PVC, EVA foam, or polyurethane: petroleum-derived materials that often contain additives to improve flexibility, texture, and durability.

The concern: phthalates.

Phthalates are plasticizers used to make materials softer and more flexible. They’ve been linked in research to potential hormone disruption, reproductive health effects, and developmental concerns, particularly for children. Some footwear products even carry warning labels about the presence of these chemicals.

Summer makes this worse. Feet sweat more, shoes sit in direct sunlight, and heat accelerates the breakdown of synthetic materials, all of which can increase the release of chemical compounds from the footwear.

What I choose instead:

• Natural rubber sandals
• Leather sandals from reputable manufacturers
• Cork-based footwear
• Going barefoot on grass, sand, or soil when practical

It’s one of the easiest swaps to make, and natural rubber or leather sandals often hold up far longer than cheap plastic ones anyway.

2. Conventional Chemical Sunscreen

Sun protection matters; excessive UV exposure increases the risk of sunburn, premature aging, and skin cancer.

Most conventional sunscreens use chemical UV filters that absorb ultraviolet radiation and convert it to heat before it penetrates the skin. One of the most common is octocrylene.

The concern: absorption and hormone signaling.

Research has shown that certain chemical UV filters, including octocrylene, can be absorbed through the skin and detected in the bloodstream after use. Regulatory agencies and researchers are actively studying the long-term health implications of this. Some studies have examined whether these ingredients may influence hormone signaling pathways, though the science is still developing.

The other issue is fragrance. “Fragrance” on an ingredient label can represent a blend of dozens or even hundreds of undisclosed chemicals. Some fragrance compounds are associated with skin irritation, allergic reactions, and potential effects in sensitive individuals, including kids.

What I choose instead: mineral sunscreen.

Mineral sunscreens use zinc oxide to create a physical barrier that reflects and scatters UV light rather than absorbing it. They typically contain fewer synthetic ingredients and avoid the chemical filters that have raised the most concern.

When shopping, look for products that:

• Use non-nano zinc oxide as the active ingredient
• Are fragrance-free
• Have short, transparent ingredient lists
• Offer broad-spectrum (UVA + UVB) protection

Badger is a widely available option that checks these boxes and is readily available at many natural retailers. Whatever brand you choose, the goal is consistent protection, just with a cleaner formula.

3. Synthetic Underwear

Underwear rarely comes up in conversations about toxic exposure. It probably should.

It’s the clothing item with the longest daily skin contact, worn against some of the body’s most absorptive areas. Yet most mainstream options, including bulk packs at Costco, are made from polyester, nylon, modal, elastane, or blended synthetics.

The concern: dyes, finishes, and microplastics.

Synthetic textiles are made from petroleum-derived materials and frequently treated during manufacturing with dyes, stain-resistant coatings, odor-resistant finishes, and other chemical additives. They also shed microscopic plastic fibers, microplastics, during washing and wear. Researchers are still investigating the health implications of chronic exposure to microplastics, but interest in natural alternatives has grown considerably as the evidence builds.

What I choose instead: organic cotton.

Cotton has been used for thousands of years for good reason. It breathes well, stays cooler, and doesn’t trap heat and moisture the way synthetics often do. Organic cotton goes further by reducing exposure to the pesticide residues commonly associated with conventional cotton production.

When shopping for underwear, look for:

• 100% organic cotton
• Oeko-Tex® Standard 100 certification
• Undyed or low-impact dyes
• Brands with transparent manufacturing practices

Organic cotton underwear is more accessible and affordable than it used to be. Several retailers now carry solid options that don’t require a specialty store.

Small Swaps, Real Impact

The logic is simple: these are products that sit directly against your skin for hours every day, often in heat and sweat. If safer alternatives exist at a comparable price point, the swap is worth making.

Replacing plastic flip-flops with natural rubber sandals, switching to a mineral sunscreen, and moving to organic cotton underwear, those three changes alone target some of your highest-contact daily exposures. Repeated over months and years, that kind of consistent reduction adds up.

Frequently Asked Questions

Are all Costco products toxic? No, many Costco products are perfectly fine, and the retailer has expanded its selection of cleaner options in recent years. The concern is with specific product categories that tend to contain synthetic chemicals, petroleum-derived materials, or additives linked to health concerns. The three covered here, plastic flip-flops, conventional chemical sunscreens, and synthetic underwear, are worth reconsidering because of their prolonged, daily skin contact.

What are phthalates, and why do they matter in footwear? Phthalates are chemical plasticizers used to make materials like PVC softer and more flexible. They’re commonly found in cheap plastic products, including many flip-flops and foam sandals. Research has linked phthalate exposure to potential hormone disruption and developmental effects, particularly in children. Heat and sunlight can accelerate the breakdown of plastic materials, potentially increasing the release of these compounds during wear.

Is mineral sunscreen actually as effective as chemical sunscreen? Yes. Mineral sunscreens using zinc oxide provide broad-spectrum protection against both UVA and UVB radiation. They work by physically reflecting UV light rather than absorbing it, and they’re considered safe and effective by most dermatologists. Non-nano zinc oxide formulas are a particularly well-regarded option for families looking to reduce exposure to chemical UV filters without compromising sun protection.

What is Oeko-Tex® certification, and does it matter for underwear? Oeko-Tex® Standard 100 is an independent certification that tests textiles for harmful substances, including dyes, heavy metals, formaldehyde, and pesticide residues. For underwear specifically, where skin contact is prolonged and direct, it provides meaningful assurance that the product has been screened for the chemicals most likely to raise concerns. It’s one of the most reliable labels to look for when choosing lower-toxic clothing.

Why is organic cotton better than regular cotton for underwear? Conventional cotton is one of the most heavily sprayed crops in the world. Organic cotton is grown without synthetic pesticides or fertilizers, reducing the potential for residues in the final fabric. For underwear that stays in contact with sensitive skin all day, this distinction is more relevant than it might be for, say, outerwear. Organic cotton is also softer and more breathable than many synthetic alternatives.

What’s the easiest first swap to make? Most people find underwear the most impactful place to start because the skin contact is so prolonged and direct. A basic pack of organic cotton underwear is widely available and comparably priced to conventional options. Sunscreen is a close second, especially for families with young children who wear it regularly throughout summer.

 

References:

1. Dueñas-Moreno, J., Mora, A., Kumar, M., Meng, X. Z., & Mahlknecht, J. (2023). Worldwide risk assessment of phthalates and bisphenol A in humans: The need for updating guidelines. Environmental International, 181, 108294.https://doi.org/10.1016/j.envint.2023.108294
2. Ruszkiewicz, J.A., Pinkas, A., Ferrer, B., Peres, T.V., Tsatsakis, A., & Aschner, M. (2017). Neurotoxic effect of active ingredients in sunscreen products: A contemporary review. Toxicology Reports, 4, 245–259.https://doi.org/10.1016/j.toxrep.2017.05.006
3. Suh, S., Pham, C., Smith, J., & Mesinkovska, N.A. (2020). The banned sunscreen ingredients and their impact on human health: A systematic review. International Journal of Dermatology, 59(9), 1033–1042.https://doi.org/10.1111/ijd.14824
4. Chatzigianni, M., Pavlou, P., Siamidi, A., Vlachou, M., Varvaresou, A., & Papageorgiou, S. (2022). Environmental impacts due to the use of sunscreen products: A mini-review. Ecotoxicology, 31(9), 1331–1345.https://doi.org/10.1007/s10646-022-02592-w
5. Palacios-Mateo, C., van der Meer, Y., & Seide, G. (2021). Analysis of the polyester clothing value chain to identify key intervention points for sustainability. Environmental Sciences Europe, 33(1), 2.https://doi.org/10.1186/s12302-020-00447-x
6. DeWitt, J. C., Goldenman, G., Lohmann, R., Ng, C. A., & Wang, Z. (2025). Emerging toxicological awareness of per- and polyfluoroalkyl substances: The rising concern over “forever chemicals.” Disease Models & Mechanisms, 18(11), dmm052647.https://doi.org/10.1242/dmm.052647