Chemical vs physical exfoliation: acids, scrubs and brushes

Walk down any skin care aisle and you’ll see two ways to exfoliate: things you rub on and things you leave on. Scrubs, brushes and textured cloths do the work by friction. Acid toners, serums and pads do it chemically. Both remove dead skin, but they get there differently, and that difference matters most if your skin is sensitive.

Two ways to remove dead skin

The American Academy of Dermatology (AAD) describes the two methods simply:

• Mechanical (physical) exfoliation uses a tool, such as a brush, pad or sponge, or a scrub to physically remove dead skin cells.
• Chemical exfoliation uses chemicals, such as alpha and beta hydroxy acids, to dissolve dead skin cells.

Physical exfoliation is instant: you rub, you rinse, the loose flakes are gone. How much it takes off depends on the grit, the tool and above all how hard you press.

Chemical exfoliation is slower and invisible. The acid loosens the bonds between dead cells over minutes to hours, and they shed on their own. How much it does depends on the acid, its strength, the product’s acidity and how long it stays on.

Neither is automatically gentler. A soft washcloth used lightly can be milder than a strong acid, and a mild acid lotion can be milder than a gritty scrub scrubbed hard.

What counts as physical exfoliation

It’s more than the jar labelled “scrub”. Your skin feels friction from:

• Scrubs with grains, seeds, sugar, salt or other particles.
• Cleansing brushes, manual or powered.
• Exfoliating gloves, mitts, sponges and textured pads.
• Washcloths, especially rough ones.
• Towelling off hard.

That’s why a routine can end up more abrasive than you meant it to be: a brush in the morning, a scrub on the weekend and vigorous towel drying every day all add up.

The “microtears” question

You’ve probably read that scrubs with crushed shells or pits cause “microtears”, tiny cuts in the skin. It’s a widely repeated idea, and it sounds plausible. But when we looked, we couldn’t find good studies that measured tears in skin from normal use of consumer scrubs. So we can’t tell you it’s proven.

What is well established is simpler: friction irritates skin. DermNet lists friction and mechanical trauma, such as hand scrubbing, among the causes of irritant contact dermatitis, a skin inflammation that damages the skin barrier, the outer layer that keeps water in and irritants out. The AAD notes that aggressive exfoliation can leave dark spots, especially on darker skin tones. And its acne advice is to wash with your fingertips, because scrubbing with washcloths, sponges and other tools can irritate skin.

In practice, you don’t need to settle the microtears debate. If a scrub feels sharp, leaves your skin red or stings afterward, it’s too harsh for you, whatever the particle.

Chemical exfoliation has its own trade-offs

Acids avoid friction, but they bring their own issues:

• They can sting, redden and dry skin, especially at higher strengths or when layered with other actives.
• Alpha hydroxy acids (AHAs), such as glycolic and lactic acid, increase your skin’s sensitivity to the sun. The US FDA notes this effect wears off about a week after stopping, but it means daily sunscreen while you use them.
• They’re easy to overuse, because you can’t see them working.

So “chemical” isn’t the safe option and “physical” the risky one. They’re different tools with different ways of going wrong.

Canada’s microbead ban

If you remember scrubs with tiny, perfectly round coloured beads, those were often plastic. Canada’s Microbeads in Toiletries Regulations, published in 2017, prohibit plastic microbeads of 5 mm or less in toiletries used to exfoliate or cleanse, including bath and body products, skin cleansers and toothpaste.

• Manufacture and import were banned as of July 1, 2018.
• Sale was banned on the same date for most toiletries.
• Natural health products and non-prescription drugs containing microbeads could be sold until July 1, 2019.

The reason was environmental, not skin safety. The government acted because plastic microbeads were getting into Canadian lakes, rivers and oceans. Scrubs sold in Canada now use other kinds of particles, and the ban doesn’t tell you whether a given scrub is gentle on skin.

Choosing if your skin is sensitive

The AAD’s guidance by skin type is a good starting point:

• Dry, sensitive or acne-prone skin may prefer just a washcloth and a mild chemical exfoliant, since mechanical exfoliation may be too irritating.
• Oily, thicker skin can often handle stronger chemical products or mechanical exfoliation.
• Darker skin tones, or anyone who gets dark marks after acne, bug bites or burns, should avoid strong chemical or mechanical exfoliation.

For acne-prone skin specifically, the AAD also suggests avoiding products that irritate, including astringents, toners and exfoliants, and washing gently with your fingertips. If you have acne and want to exfoliate, talk to your pharmacist or doctor about what fits with any acne treatment you’re using.

A few more tips for sensitive skin:

• Pick one method, not both.
• If you use a scrub, choose a fine, soft texture, use light pressure for about 30 seconds, rinse with lukewarm water and moisturize right away, as the AAD suggests.
• If you use an acid, start with a low strength a couple of times a week.
• Skip both on sunburn, broken skin or an eczema flare.

You can browse the panel’s reviewed exfoliators or filter for products suited to sensitive skin. If your skin stays red, stinging or flaky after you stop exfoliating, see your doctor or pharmacist.

The short version: scrubs, brushes and acids all exfoliate; they just take different routes. The microtears scare is more repeated than proven, but friction is a known irritant. Plastic microbeads are gone from Canadian shelves for environmental reasons. For sensitive skin, gentle and occasional beats strong and frequent, whichever method you choose.