Dry shampoo and your scalp: handy, but not a real wash

Dry shampoo has rescued plenty of mornings: after the gym, on a camping trip, the day after a blowout you’d rather keep. It’s genuinely useful. But the name promises more than it delivers, and how you use it makes a real difference to your scalp. Here’s what it does, where its limits are, and what the recent recalls were about.

What dry shampoo actually does

Dry shampoo doesn’t wash anything. It absorbs oil. Cleveland Clinic dermatologist Wilma Bergfeld explains that the alcohol or starch in these products soaks up excess oil and grease, which gives hair a cleaner, fresher look and often a bit of volume.

Most products fall into two groups:

• Aerosol sprays, which use a propellant gas to blow a fine mist of absorbent powder and alcohol onto the hair.
• Loose or tinted powders, which you shake or brush in, with no propellant.

Either way, the oil doesn’t go anywhere. It’s soaked into a powder that then sits on your hair and scalp until you brush it out or wash it away. That’s the key difference from regular shampoo, which uses surfactants and water to lift oil, sweat, shed skin cells, product residue and microbes off the scalp and rinse them down the drain.

Why it can’t replace washing

Your scalp is skin, and busy skin at that. It makes oil, sheds cells and hosts a yeast called Malassezia that feeds on that oil. A wet wash resets all of that. Dry shampoo only hides the oil.

The American Academy of Dermatology (AAD) is clear that dry shampoo shouldn’t replace regular shampooing. It suggests washing with shampoo and water after one or two uses of dry shampoo. The Cleveland Clinic article makes the same point: occasional use, not several days in a row.

What build-up does to your scalp

When dry shampoo is used day after day without a proper wash, powder, absorbed oil and dead skin pile up. That’s where the problems start.

According to the AAD and the Cleveland Clinic:

• Irritation and itch. Build-up can leave your scalp itchy, burning or tender.
• Clogged follicles. The Cleveland Clinic links heavy build-up to blocked pores and folliculitis, an inflammation of the hair follicles that shows up as small, tender bumps or pimples.
• Flaking. The AAD warns that using only dry shampoo and skipping regular washing can lead to seborrheic dermatitis, an itchy, scaly rash. If you’re already prone to dandruff, the extra oil and debris give the yeast more to feed on.
• Breakage and shedding. The AAD says dry shampoo left on the hair and scalp can contribute to hair breakage and shedding. The alcohol in some sprays can also dry out strands.

None of this means dry shampoo is harmful when used as intended. It means it has to be washed out.

The AAD also advises against homemade versions, such as kitchen starch or powder mixtures, because they can clump, show in your hair and clog pores.

The benzene recalls, explained

In December 2021, Health Canada announced a recall of aerosol dry shampoo and dry conditioner sprays from one manufacturer after benzene was detected; about 800,000 units had been sold in Canada. In October 2022, a second manufacturer recalled certain lots of aerosol dry shampoo, covering more than 1.5 million units sold in Canada between 2020 and 2022, with a parallel recall in the United States.

Benzene is a chemical classified as a human carcinogen, meaning it can cause cancer with enough exposure. It isn’t an ingredient in dry shampoo. In the US recall notice posted by the Food and Drug Administration (FDA), the company said an investigation traced it to the propellant, the pressurized gas that pushes the product out of the can.

How worried should you be? Health Canada’s recall notices say that daily exposure to benzene in the recalled products, at the levels found in testing, would not be expected to cause adverse health effects. The recalls were a precaution to remove contaminated lots, and no injuries were reported in Canada as of the 2022 notice. If you still have an old aerosol can, you can check Health Canada’s recalls and safety alerts website to see whether it was affected.

If you’d rather avoid the question altogether, powder dry shampoos don’t use a propellant.

Using dry shampoo well

The AAD’s tips for getting good results without scalp trouble:

• Use a small amount, only where your hair looks greasy, usually at the roots and hairline. You can always add more.
• Spread it evenly over the scalp, leave it on for as long as the label says, then brush or comb it out.
• Wash your hair with regular shampoo and water after one or two uses.
• Stop if your scalp becomes irritated. If irritation lasts several weeks, see a dermatologist.

A few common-sense habits help too. Spraying in a ventilated room means you breathe in less of the mist. Keep it off an already flaky or inflamed scalp. And if dandruff is a problem, an anti-dandruff shampoo on wash days will do far more for you than any dry shampoo between them. You can browse hair care products to compare wet and dry options.

When to see a doctor

See your doctor or pharmacist if you develop an itchy, scaly or bumpy scalp that doesn’t settle after you stop using dry shampoo and go back to regular washing, if you notice more hair shedding than usual, or if there are painful, pus-filled bumps. Folliculitis, seborrheic dermatitis and contact dermatitis (a rash from something that touched the skin) can all start this way, and each is treated differently.

The bottom line: dry shampoo is a handy bridge between washes, not a wash. Use a little, brush it out, and wash your hair properly after one or two uses. The benzene recalls were about contaminated aerosol propellant in specific lots, not about dry shampoo as a category, but powders are there if you’d rather skip aerosols.