The Difference

“Soaps” and “detergents” are two different types of cleaning agents known as “surfactants.”

“Soaps” have been made for thousands of years through a process called “saponification.” The process is fairly simple. Acids (e.g., fats, oils) are combined with a base, and as the two react, the oils are saponified. Historically, the base for the reaction was derived from wood ashes. Today, soapmakers generally use sodium hydroxide (for solid soap) or potassium hydroxide (for liquid soap). When done properly, these ingredients are fully consumed by the reaction so that none remains in the final soap product.

By contrast, “detergents” are synthetic surfactants and are relatively new. They were first developed in the early part of the 20th century due to war-time shortage of fat and oil supplies, and they became increasingly prevalent after World War II. Detergents can be synthesized from a wide range of starting materials, including petroleum products, as well as “natural” or “plant-based” materials.

Today, detergents dominate store aisles. Even products that have “soap” in the name are often detergents in disguise—the only way to discern the difference is by reading the ingredients. Unless you’ve intentionally been avoiding them, detergents are likely in nearly every personal care and home cleaning product that you own.

Common detergent-based products include: hand “soap,” dish “soap,” dishwasher detergent, laundry detergent, lotion, shampoo, body wash, toothpaste, cleaning products, makeup, lip balm, deodorant, and even lawncare and pet care products.

In short, you put detergent on your skin, you eat detergent residue off your kitchenware, and you inhale detergent residue in your household dust.

But we can change that—starting in our own homes. We’ll come back to that in a minute.

Why It Matters

(Sources are listed at the bottom of this page.)

Harsh detergents have been shown to weaken the skin barrier, increasing its permeability and allowing things that should stay in (like moisture) to come out, and allowing things that should stay out (like allergens, bacteria, and chemicals) to come in. This effect on membrane permeability applies to lung and gut health, as well, when we ingest and inhale detergent residues.

This matters, because barrier disfunction (another way of saying a weakened barrier, or a more permeable barrier) of the skin, lungs, and gut is associated with eczema, food allergies, asthma, and autoimmune disorders, as well as autism, Alzheimer’s disease, and depression.

A number of recent studies reach this conclusion, including a 2023 study involving Dr. Kari Nadeau, a world-renowned expert in pediatric food allergies and asthma. This study found that exposure to laundry detergent residue in clothing causes skin barrier damage, which plays a critical role in the development of allergic, metabolic, and autoimmune disorders [1]. The blog offers a deeper dive into this study.

This study is part of a growing body of work around the “Epithelial Barrier Hypothesis,” which proposes that barrier disfunction of the skin, lungs, and gut (as well as other tissues) is caused by laundry and dishwasher detergents, household cleaners, and surfactants, among other things, and that this plays a role in many chronic diseases, including eczema, food allergies, asthma, and autoimmune disorders, as well as autism, Alzheimer’s disease, and depression. [2]. The blog offers more on the epithelial barrier hypothesis.

Before we go any further, let’s be clear—we are not saying that soap is a “cure” for health maladies. We are saying that harsh detergents are a culprit.

Additionally, not all detergents are created equal—some are harsher than others. Similarly, not all soaps are created equal. Ingredients matter. Which brings us to the next important point . . .

Detergent-based products often include a lot of other junk, like preservatives, fragrance, dyes, and other harsh chemicals that are each independently harmful to people and the earth.

To put it another way, we are called “Start with Soap.” But a more accurate—albeit slightly less catchy—name might have been, “Start by Eliminating Detergents and All the Other Junk That Often Goes With Them.”

Finally, there is some emphasis on the word “Start” here. Harsh detergents are one aggravating factor amidst many others. But the reason this is such a powerful place to start is because it is so simple and so directly within our control. And when a problem feels too huge and too overwhelming to tackle, you chip away at it one little bit at a time.

So give yourself plenty of space and grace, and make your first step a simple one—Start with Soap.

Start with Soap for . . .

Here’s a sneak peak at what it looks like to use soap for different applications in your home.

Handwashing

Switching to soap for handwashing couldn’t be easier. Grab a bar of soap, or fill a foaming hand dispenser with a soap flake solution, and set it next to your sink.

Laundry

Our skin is in constant contact with our clothes, which means it is in constant contact with laundry detergent residue. This perpetual exposure, day in and day out, adds up!

Fortunately, switching to soap (and ditching harsh detergents and other chemicals) couldn’t be easier—simply substitute soap flakes, baking soda, and washing soda (our laundry powder is pre-mixed and ready to go!) into your current laundry routine.

And don’t fret about cleaning performance here—soap works! So many people who identify as “sweaty and stinky” are amazed by how well soap cleans the grossest of gym clothes—even better than the detergents they used previously.

Dishwashing

We ingest small amounts of the products we use to clean our dishes. So let’s avoid junk we’d never consciously choose to ingest.

For washing dishes by hand, use the exact same foaming soap dispenser that you use for washing hands at the kitchen sink.

The dishwasher is a bit of an outlier—we have never gotten a true soap to work quite right (if you have, let us know!). Instead, we offer a minimalist dishwasher powder at the store.

Home Cleaning

You do not need harsh chemicals to clean your home.

Soap, baking soda, and vinegar—you will be amazed at what these three simple products can do.

You just need to know which one to use in which circumstances. And that’s exactly what we’ll share.

Personal Care

This category is different for different people, because it’s—well—personal.

Ready to use soap for washing bodies, but not ready to change your hair care? No problem. Ready to ditch everything in your bathroom cabinet and go all in? We’re here for that, too.

So we’ll meet you where you are, wherever that may be, and offer suggestions for dropping or swapping items in your routine.

Sources

[1] Arturo Rinaldi et al., Household laundry detergents disrupt barrier integrity and induce inflammation in mouse and human skin, 79 Allergy 128 (2023).

[2] Cezmi Akdis, Does the epithelial barrier hypothesis explain the rise in allergy, autoimmunity and other chronic conditions? 21 Nat. Rev. Immunol. 739 (2021). See also Cezmi Akdis, The epithelial barrier hypothesis proposes a comprehensive understanding of the origins of allergic and other chronic noncommunicable diseases, 149 J. Allergy Clin. Immunol. 41 (2021).

[3] A.J. Lumsdaine, Eczema: One Family’s Solution, http://solveeczema.org. See also A.J. Lumsdaine & J.C. Ross, Abnormal Amplification? Observations from Applying the Engineering Method to Solving Eczema and Atopic Disease, The Winnower (2017), available here.