Dry shampoo

Key takeaways

• Dry shampoo absorbs oil; it does not clean. Typical products are powders or aerosols containing starch, clay or silica that soak up sebum so roots look and feel less greasy and hair has more lift. It does not remove dirt, flakes or product, so you still need to wash.
• Published evidence is thin. PubMed returns only a handful of dry-shampoo papers: a 1964 report on a dry shampoo for oily seborrhea, a 2021 research letter on contact allergens in dry shampoo products (Newell 2021), and unrelated studies. We found no trial of hair or scalp health outcomes with regular use.
• The main documented safety problem is contamination, not routine use. In October 2022, Unilever recalled aerosol dry shampoos made before October 2021 after benzene, a known carcinogen, was found. The company traced it to the propellant and said daily exposure at the detected levels would not be expected to cause harm. Independent testing results differed between batches and products.
• Contact allergens are present in some dry shampoos (Newell 2021). Which allergens and how many is not available from the abstract.
• Overuse can plausibly build up on the scalp, especially one prone to dandruff or folliculitis, but this is unstudied. Washing remains the way to remove it.
• Dry shampoo is not a treatment for an oily scalp. It masks oil; see washing frequency.

The science

Sebum builds up on a predictable schedule and the scalp does not make more oil because you wash more, so powders simply adsorb surface oil. Aerosol products add propellants (hydrocarbon gases such as butane and isobutane), and the purity of these became the issue in 2022.

What it means by hair profile

• Fine, straight, oily hair: where dry shampoo is used most, for volume and for stretching the time between washes.
• Dark hair: white powders leave a grey cast; tinted powders exist.
• Curly and coily hair: heavy powders can dry and tangle strands, and most coily hair needs less oil removal anyway.
• Dandruff, folliculitis or sensitive scalps: avoid layering powders on inflamed skin; wash and treat first.
• Thinning hair: powders can add the look of density temporarily; see thinning hair styling.

Myths and facts

• Myth: dry shampoo cleans the scalp. Fact: it absorbs oil only.
• Myth: it causes hair loss. Fact: no evidence; buildup with inflammation is the theoretical concern.
• Myth: all aerosol dry shampoos contain benzene. Fact: the 2022 recall covered specific batches.
• Myth: it replaces washing indefinitely. Fact: wash at least as often as your scalp needs.

Bottom line

Use it sparingly, hold aerosols at a distance, avoid inhaling, and brush out thoroughly. Check recall lists for your product if you use aerosols often. Do not use it on an irritated or flaky scalp; wash and treat first. Limit it to a few days between washes, and wash thoroughly afterwards.