LA Poor Air Day: Why Ozone Is Not Soot, and What That Means for Your Routine

Los Angeles was flagged for poor air quality in our environmental feed on November 7, 2026. Most skin advice about bad air days talks about smoke and soot. But the pollutant that defines a typical smoggy LA day is different: ground-level ozone, a gas you cannot see, wipe off or rinse away. That changes what a routine can realistically do, so it is worth separating the two.

Ozone and particles are not the same problem

The EPA's AirNow system uses one color scale for both. Orange covers index values of 101 to 150, red 151 to 200, purple 201 to 300 and maroon 301 and above, and the same table applies to ozone and to particle pollution. The agency reports five regulated pollutants on this scale, including ground-level ozone and particle pollution (PM2.5 and PM10).

The color tells you how bad the air is, not what is in it. Particles are tiny solids and droplets that can settle on skin and hair, which is why a gentle evening cleanse makes sense after a smoky day. Ozone is a gas. It is not something you can see on a washcloth, so cleansing does not remove it in the same way. When you check an air quality app, look for which pollutant is driving the number, because the practical advice differs.

What ozone does at the surface of skin

The most useful research on ozone and skin comes from the lab of Giuseppe Valacchi and colleagues. Their review in the British Journal of Dermatology describes how ozone is too reactive to travel deep into tissue. Instead it reacts with the outermost layer, depleting antioxidants there, and that in turn sets off responses in the deeper layers of skin. The same review notes a twist: ozone is also used in controlled medical settings, and the authors conclude it can be damaging with long exposure and beneficial with brief, controlled exposure. That second point is about clinical use, not about the smog outside your door, and nothing in it suggests breathing urban ozone is good for skin.

A 2002 paper by Packer and Valacchi identifies vitamin E as a key indicator of this stress. It is described as the main antioxidant in mouse and human skin, with lower levels in the outer stratum corneum, and in the experiments they summarize, combining UV and ozone produced a larger drop in vitamin E than UV alone would predict. In plain terms, sun and ozone together appear to use up the skin's own defenses faster than either one separately.

Why the sun matters on a smog day

Ozone forms when sunlight drives chemical reactions in polluted air, so the days with the worst ozone are usually bright days. That combination is exactly the one the research flags. If the pairing of UV and ozone depletes surface antioxidants faster, then sunscreen is the first and best lever on a poor air day, not an optional extra.

Practical steps for the morning:

• Apply a broad-spectrum sunscreen as the last step, using the amount your product's label directs.
• Reapply if you are outdoors for long stretches, following the label.
• Wear a hat or sit in shade where you can, since these do not depend on any ingredient claim.

Where antioxidant serums fit, and where the evidence stops

A 2018 review by McDaniel, Farris and Valacchi summarizes how UV light, visible light, infrared radiation and ozone damage skin mainly by generating reactive oxygen species, and it discusses sunscreens and topical antioxidants as protective strategies. That supports the logic of layering an antioxidant under sunscreen. It does not show that a particular serum on a particular LA afternoon will change how your skin looks.

Be careful with the vitamin E numbers. The experiments behind the 2002 summary were done in mouse skin using ozone exposures in a chamber, and a chamber dose is not the same thing as walking to a train in a smoggy city. Treat the work as a mechanism, an explanation of why antioxidants are a sensible idea, rather than proof of a result. We have not found a head-to-head human trial in the sources we reviewed that tells you how much a topical antioxidant changes visible outcomes on a high-ozone day, so we will not invent one.

If you want to try an antioxidant step, a few conservative rules apply:

• Choose one antioxidant product at a time so you can tell how your skin responds.
• Patch test on the inner forearm or behind the ear for several days before using it on your face.
• Keep the rest of the routine boring: cleanser, moisturizer, sunscreen.

Don't over-correct with harsh cleansing

It is tempting to scrub harder after a pollution warning. The risk is a stinging, tight feeling that signals a stressed barrier, which leaves skin less comfortable for days. Since ozone acts on the outermost layer, the goal is to keep that layer in good condition, not to strip it. Use a mild, fragrance-free cleanser once in the evening, rinse with lukewarm water, and follow with a moisturizer that suits your skin type.

A simple plan for a poor air day in LA

Here is a short checklist you can run in under five minutes:

1. Open an air quality map and note whether ozone or particles are the main pollutant. The color scale on AirNow is the same for both, so the pollutant name is the detail that matters.
2. In the morning, finish with sunscreen. This is the step with the strongest logic behind it given the UV and ozone findings.
3. If you already use an antioxidant product and it agrees with your skin, keep it under your sunscreen. If you do not, there is no need to start one today.
4. In the evening, cleanse gently and moisturize. Skip new actives on a day when your skin already feels reactive.
5. If you spend time outdoors, check the official health guidance for your air quality level, because it covers breathing as well as skin.

The takeaway

Ozone is a surface-reactive gas, which makes it a different problem from soot. The research summarized here points to the outer layer of skin and its antioxidant defenses, and it suggests sun exposure compounds the effect. For a day when LA air is rated poor, the dependable routine is simple: sunscreen in the morning, one well-tolerated antioxidant if you like, a gentle cleanse and a moisturizer at night. Anything more elaborate needs better human evidence than currently exists in the sources we reviewed. Where your skin looks or feels persistently irritated, talk with a dermatologist or your doctor.