What “Non-Toxic” Actually Means

A Course by Interior Medicine

Dr. Meg Christensen is the founder of Interior Medicine, a physician-created resource on non-toxic home products and household exposures. Her layer-by-layer analysis of materials and products draws on her background in medicine, biochemistry, epidemiology, and clinical research.

Published March 2026 | Updated March 2026

What “Non-Toxic” Actually Means is a deep-diving, visual, and completely free curriculum about how to evaluate materials, products, brands, and the non-toxic advice circulating online.

There is no standard definition of “non-toxic” yet, for good reason: it's complicated. But it's time to start defining it, because some brands misuse that ambiguity to their advantage, because population-level health patterns suggest something is shifting in our environment, and because not having a definition yet isn't the same as not needing one. I propose a definition in Part 12 that builds off of each of the parts in the course.

The course is both practical and philosophical. You’ll finish knowing how to evaluate anything, but it will also make you think about how you think about risk, navigate uncertainty, and find balance in a contentious wellness landscape. My hope is that it’s mind-expanding, and an antidote to fear and polarization. When you finish, I hope you feel calm, anchored, and empowered.

Here’s what it covers:

Course CurriculumWhat “Non-Toxic” Actually Means: A Course by Interior Medicine
Course Curriculum

        13 parts
      
        Self-paced
      
        Free
      
Intro + Parts 1–3
The Foundations
The thinking tools you'll use for the rest of the course and beyond. These three sections give you a framework for assessing risk, understanding what chemicals actually are, and reading research critically. Everything else in the course builds on these three sections.
0
Why “Non-Toxic” Has No Real Definition
Why nobody agrees on what “non-toxic” means, and why that's actually the most useful place to start.
01
A Framework for Assessing Any Health Risk
The core toxicology framework that underlies everything else in the course.
02
The Hidden Chemistry of Home Products
How to “see” every chemical in every layer of every product: VOCs, sVOCs, and everything in between.
03
Separating Good Science From Recycled Fear
Why legitimate-looking research contradicts itself, and how to tell which study is actually right.

Parts 4–6
The Science of Exposure
What's actually in your home, how it gets into your body, and what your body does about it. This is the most concrete section of the course, based in physiology.
04
What Your Home Exposes You To
Not a random list, but one built from what WHO, IARC, and major health agencies say actually deserves concern.
05
How Exposures Reach You
We are neither completely porous nor completely protected. How your body lets things in, and keeps them out.
06
What Your Body Does With Exposures
What your organs do to protect you, where they fall short, and what bioaccumulation actually means.

Parts 7–9
Uncertainty
This is where the course gets philosophical. How we deal with uncertainty is, I believe, the crux of the wellness-versus-conventional-medicine debate. These sections dig into why it exists and what to do about it.
07
Why Most Risks Are Still a Question Mark
Understanding what we don't know, and why it's more useful than pretending we do.
08
Why Smart People Disagree on the Same Facts
Why reasonable, informed people land on completely opposite sides of the same evidence.
09
Why We Choose Feelings Over Evidence
How society, outrage, and feelings win out over data, and what that means for “non-toxic.”

Parts 10–12
Navigating Claims
With the science and the uncertainty laid out, these sections turn to the real world: the brands selling to you, the advice circulating online, and finally an actual answer to the question this course started with.
10
Spotting Healthy Brands vs. Healthwashing
How to tell the difference between a brand doing the work and one using “non-toxic” as misleading marketing.
11
Making Sense of Conflicting Non-Toxic Advice
How to evaluate sources, spot fear-based content, and hold multiple valid perspectives at once.
12
So, What DOES “Non-Toxic” Mean? An Answer.
A visual guide that finally answers the question for you and your real-life context.

The finish line
Graduation
Calm, anchored, and equipped to evaluate anything.

Read more below, or get started now‍ ‍➜

Why I Made This

Over five years of running Interior Medicine, I’ve spent a lot of time answering questions — “Is this toxic? Is this non-toxic?” and reading social media comments — "that's actually toxic, how dare you say it's safe!" and, "that's not toxic at all, how dare you say it is!" on my account, and others. That's what this course is about: what "non-toxic" actually means is a complicated question that deserves a real answer.

Most of us never learn how to evaluate health claims, read research, or think about chemical risk. For a long time, leaving that to the experts was fine. But that gap is getting more consequential as environmental toxins, and the national conversation about them, become a bigger part of all of our lives. I wanted to create an accessible, rigorous, and interesting way to help fill that gap.

Misinformation about non-toxic living is widespread, but so is the reflexive counter-reaction: dismissing any concern as wellness hysteria. There is very little useful middle ground, and very few qualified people taking the time to explain the nuances. Part of what makes this worse is that healthwashing is accelerating: brands have figured out that people care about this, and "non-toxic" has become a marketing term with no standard definition. It is my firm belief that hard science and open-mindedness about health aren't opposites. There is a rational middle way, and it matters that we find it before the conversation gets any more polarized than it already is.

My own non-toxic living arc started with deep skepticism of anything “wellness,” then became earnest zealousness, and finally has settled, over decades and a lot of formal training, into something much more balanced. I hope this course helps accelerate that process for you, and that by the end you don't need me, or anyone else, telling you what is or isn't toxic.

This curriculum has been percolating through my mind in some for or another for a long time now, and ultimately stems from my 20 years of experience across research, medicine, and design. It feels urgent to share now more than ever, and it’s something I’ve poured a lot of time and heart into. I really hope you enjoy it.

A Quick Note on Language

You might notice I use the words non-toxic, chemical, toxin, and toxic on Interior Medicine even though this course rests on the fact that there is no agreed-upon definition of the term non-toxic yet. Everything, even water, is made of chemicals, so nothing is truly chemical-free. Likewise, toxin refers to a natural substance like a plant poison or venom, whereas toxicant is a more accurate term for the chemicals in products that have a negative health impact. I recognize that something that is toxic does not automatically make it a health risk.

I choose to use these scientifically inaccurate words anyway purely for practical purposes, for now. These words are currently the most culturally agreed-upon, descriptive, and accessible terms that allow people to find the information they’re looking for. Accurate terminology is important, which is why this note, and this course exists. Let’s go!

Next: Intro: Why “Non-Toxic” Has No Real Definition ➜