High-AQI days: what smog does to your skin, and a routine that helps

Every year around Diwali the air over Delhi and the NCR thickens, the AQI crosses into the poor and very poor bands, and dermatologists' waiting rooms fill with the same complaints: dryness, dullness, breakouts and irritation, often all at once. That combination is not a coincidence. It is what a weakened skin barrier looks like. Here is what smog does, and the routine we would keep from October to February.

What is in the air

Smog is not one thing. The parts that matter for skin are particulate matter, the fine particles called PM2.5 and PM10 that come from vehicles, construction dust and burning; nitrogen oxides from traffic; and polycyclic aromatic hydrocarbons, the soot compounds from combustion that attach to particles and then to skin. India's National Air Quality Index runs from good, up to 50, through satisfactory, moderate, poor and very poor, to severe above 400. Delhi spends much of the winter in the last three bands.

Indoor air is not exempt. Cooking smoke, incense and the outside air that comes in through every gap all add to the load, which is why people who stay in on bad days still see it on their skin.

What it does to skin

Particles settle on the skin's surface and into pores. The soot compounds attached to them generate reactive molecules that the skin has to neutralise, and when it cannot keep up, the result is oxidative stress. That has three visible effects.

• The barrier weakens. Water leaves the skin faster, so it feels tight and rough even in a humid week.
• It reacts. Redness, itch and flare-ups of existing conditions become more common, and clogged pores turn into breakouts.
• Over years, it ages. Long-term studies of women living near busy roads found more pigment spots and deeper lines than in women with cleaner air, after accounting for sun and age.

The last point is why the smog months matter beyond the season. The particles do their slow work on collagen and elastin alongside ultraviolet light, and the two together are worse than either alone. Hair and scalp show the same pattern in the same months: itch, greasiness and more shedding, for the same reasons.

The smog-season routine

Nothing here is new. The order and the emphasis change.

1. Morning: a light cleanse. Water or a mild cleanser. The night's work is done; you are starting fresh.
2. Morning: an antioxidant. A vitamin C serum gives the skin help with the reactive molecules the day will produce.
3. Morning: a barrier hydrator. This is where our Damn Dewy sits: hyaluronic acid at several molecular sizes, so it holds water at more than one level, with a blue LED sonic cap we use for even application.
4. Morning: sunscreen, every day. Haze scatters light; it does not block the ultraviolet that breaks collagen down. Broad-spectrum, and reapplied if you are outdoors.
5. Evening: the most important step. If you wore sunscreen or makeup, cleanse twice: an oil or balm first to lift what the day left, then a gentle water-based cleanser. This is where the particles come off.
6. Evening: hydrate again, then your usual actives. Keep exfoliating acids to once or twice a week at most; a stressed barrier does not need more removed.

What not to do

• Do not scrub. Physical exfoliants on an already weakened barrier trade one problem for two.
• Do not skip sunscreen because the sky looks grey. Ultraviolet light is still coming through.
• Do not add five new anti-pollution products. The label is marketing. Cleansing, hydration, an antioxidant and sunscreen already cover what those products claim.
• Do not wash your face more than twice a day. Over-cleansing removes the skin's own protective lipids.
• Do not rely on makeup wipes at night. They move particles around more than they remove them.

Smog season is a barrier problem before it is anything else. Protect the barrier and most of the rest sorts itself out.

When to see a dermatologist

If you have eczema, rosacea or psoriasis, expect flares and talk to your dermatologist before the season about a plan. See one during the season if a rash lasts more than a week, if breakouts turn painful, or if itch stops you sleeping. An air purifier in the bedroom is worth considering too: skin repairs overnight, and cleaner air for those hours helps. It does not replace the evening cleanse.