Think Dirty App Review: What the 'Dirty Meter' Really Measures

Think Dirty's Dirty Meter rates beauty products on a scale that tops out at 10, judging only an ingredient's documented links to cancer, reproductive or developmental harm, and allergy or immune effects. By default a product scores no better than its worst ingredient, and anything listing "fragrance" gets 7 or higher. So the meter measures which flagged ingredients a product contains, not how risky it is at the amount used.

Below we go through how the rating is calculated, what the app rates as "dirty," how big its database is, how the shop and brand partner program work, what Premium costs, and how to read an ingredient list on the evidence instead. This review is based on Think Dirty's own methodology, FAQ and store listings, checked in October 2026. We didn't test the app hands-on.

Is there a better alternative to Think Dirty?

If what you really want to know is whether a product suits your skin, Pori takes a different approach. We make Pori, so read this with that in mind. Its ingredient scanner (Pro) flags each ingredient as beneficial, use with caution or avoid for your skin type, using fixed rules over about 250 curated INCI ingredients, and the app's selfie scan tracks hydration, texture and tone so you can see how a product actually performs. Think Dirty has a much bigger North American database, an Android app and cheaper plans, so for checking products against a chemical avoid-list it covers more ground. For other options, see our Think Dirty alternatives.

How is the Dirty Meter calculated?

Each ingredient is rated by how strong the published evidence is for three kinds of harm, according to Think Dirty's methodology page (archived April 2026). The evaluations are done by its chemistry team and advisory board, using public data from non-profit and government agencies.

Three rules turn those ingredient ratings into a product rating:

• Worst ingredient wins. A product's rating is no lower than its highest-rated ingredient, and if several ingredients rate high, the product is automatically a 10.
• Fragrance is at least a 7. Because fragrance blends aren't disclosed, any product that lists "fragrance" is rated 7 or higher.
• A few exceptions. If ingredients rated 4 to 7 make up less than 5% of the formula, or the product is certified by a recognized certifier, the rating may be reviewed case by case.

The methodology also says plainly that assigning numbers to study results is "necessarily a subjective process," and that the ratings are for information only, not medical advice.

What does Think Dirty rate as "dirty"?

A broad list of common cosmetic ingredients lands near the top of the scale. Think Dirty's FAQ (last updated in 2018, so the details may have shifted) says it rates BHA and BHT, PEGs, petrochemicals, parabens, phthalates, formaldehyde-releasing agents, siloxanes, sulfates, fragrance and non-biodegradable ingredients 8 to 10, "no matter how high or how low of a concentration is present." The stated reason is that people use many products and that combined, long-term exposure is unknown.

That's a values position, and the same FAQ notes that "the ratings are strictly based on our own interpretation."

Is the Think Dirty app reliable?

It's reliable as a record of which ingredients Think Dirty objects to, and much less reliable as a measure of risk. The app grades most of those ingredient families at the same level regardless of dose, and several of them have been reviewed by regulators or dermatologists and found acceptable as used.

• Parabens: the FDA says it does not have information showing that parabens as they are used in cosmetics have an effect on human health. See our guide to whether parabens are bad.
• Petrochemicals and siloxanes: petrolatum is a petrochemical and dimethicone is a silicone, so both fall into families the FAQ rates 8 to 10, though each is widely used in moisturizers. Our explainer on dimethicone and silicones covers what the evidence says about them on skin.
• Pore-clogging claims: a dermatology re-evaluation found that finished products made with comedogenic ingredients are not necessarily comedogenic, because many ratings came from animal tests of raw ingredients.
• "Clean" substitutes: a 2023 review in Current Dermatology Reports found no conclusive evidence of harm for many ingredients the clean movement targets, and warned that replacing them may increase use of more allergenic ones.

The app has a real point on fragrance. DermNet describes fragrance allergy as second only to nickel allergy as a cause of allergic contact dermatitis, found in around 10% of people who are patch tested. If you have eczema or reactive skin, flagging fragrance is useful. Still, the rating can't tell a fragrance-allergic person from someone who has used the same perfumed cream for years without trouble.

The bigger issue is framing. A 10 sits beside words like "toxic" and "dirty," which reads as danger, when it often means a common preservative or emollient is present at a concentration regulators allow. If you've ever thrown out a product your skin liked because it scored badly, that's the cost of the framing.

How big is the Think Dirty database?

Its Google Play listing says the database has over 850,000 cosmetics and personal care products from Canada and the U.S. as of October 2026. Coverage outside North America is thinner; the listing says the small team is still working through submissions, especially from EU users. When a product is missing, you can photograph its barcode and ingredient list to submit it, and you can upvote unrated products so the team asks brands to get them verified. Products without enough data show as "ingredients not yet rated."

How do the Think Dirty shop and brand partners work?

Think Dirty makes money from users and from brands, and it's open about both. Here is what its own pages and listings describe.

• Shop Now: the Play listing says you can buy products directly from Amazon, Well.ca and Sephora from inside the app.
• Ads: both the App Store and Google Play listings say the app contains advertising.
• Verified Brand Partners: brands can apply for a verification service that adds a checkmark badge, the right to use the Think Dirty rating in their marketing, and a shop button linking to the brand's site. Listed extras include in-app marketing, beauty box sampling and affiliate partnerships.
• Rating updates: the partner FAQ says brands cannot pay to improve their ratings with false information, but can supply extra details, such as fragrance components, to make a rating more accurate. Updating a listing carries a one-time fee, and a partnership isn't required.
• Awards: the Dirty Thinkers' Choice Awards are voted on by users, and brands purchase entries to be included.

None of this proves ratings are bought, and Think Dirty says they aren't. It does mean the brands that pay for visibility are the ones a "dirty" rating pushes you toward, so treat the shop and badges as advertising and the meter as one opinion.

How much does Think Dirty Premium cost?

The app is free to download, with Premium and All Access tiers. The US App Store lists these in-app purchases as of October 2026, without saying which billing period each price covers.

The app rates 4.8 from about 57,000 US App Store ratings and needs iOS 16 or later. Its App Store privacy label says data including purchases, location, search history and identifiers may be used to track you.

How can you read ingredients on the evidence instead?

1. Start with your own history. If your skin has reacted to something before, that ingredient matters more than any app score. A dermatologist can patch test you to find out exactly what it is.
2. Look for the purpose of each flagged ingredient. A preservative keeps a water-based product from growing mold and bacteria, and leaving it out isn't automatically safer.
3. Check what regulators say about the dose. Safety bodies publish opinions on common ingredients and set limits by concentration. The EU's safety committee, for example, judged phenoxyethanol safe as a preservative at up to 1.0%.
4. Separate allergy from toxicity. Fragrance and some preservatives can cause allergic reactions in some people. That's different from long-term harm to everyone.
5. Test before you commit. Our patch test guide shows how to try a product on a small area first.

For a head-to-head with the other big hazard scanner, read Yuka vs Think Dirty.

Who is Think Dirty best for?

It suits people who already follow a clean-beauty avoid-list and want a fast way to apply it in North American stores, and people avoiding fragrance or a known allergen who can set alerts. It's a weaker fit if you want to know whether a product will help your acne, dryness or dark spots, because the meter scores only potential harm. If a product causes burning, swelling or a rash, stop using it and see a dermatologist.