Fact-Checking Methodology
How we verify claims, assess evidence quality, and maintain data accuracy across the site.
Source hierarchy
We evaluate sources based on the strength of their methodology. Higher-level evidence takes precedence when sources conflict. Here is the hierarchy we follow, from strongest to weakest:
Systematic reviews & meta-analyses
Pool data from multiple studies. These provide the strongest evidence because they synthesize findings across research teams, sample sizes, and methodologies. A well-conducted systematic review carries more weight than any single study.
Example: A Cochrane review analyzing 15 RCTs on AHA efficacy for photoaging
Randomized controlled trials (RCTs)
The gold standard for individual studies. Participants are randomly assigned to treatment or control groups, reducing bias. We note sample size, duration, and whether the study was blinded.
Example: A double-blind RCT comparing 10% glycolic acid vs placebo over 12 weeks in 60 subjects
Cohort & case-control studies
Observational studies that follow groups over time or compare groups retrospectively. Useful when RCTs are impractical or unavailable. We note that these cannot establish causation, only association.
Example: A 5-year follow-up of patients using glycolic acid peels for acne scarring
Case series & case reports
Reports on individual patients or small groups. Valuable for identifying adverse reactions, rare outcomes, or novel applications. We do not use these as sole support for broad clinical claims.
Example: A case series of 8 patients showing improvement in melasma with glycolic acid peels
Expert opinion & clinical guidelines
Statements from recognized authorities (AAD, BAD, EADV) and textbook knowledge. Used for context, standard-of-care information, and when higher-level evidence is unavailable. We always note that this is expert opinion, not empirical evidence.
Example: AAD guidelines recommending patch testing before starting any new acid product
How claims are verified
Every factual claim in our articles goes through a verification process:
- Identify the claim. Each statement of fact is flagged during writing. Opinions, common knowledge, and subjective observations are handled differently from empirical claims.
- Find the primary source. We locate the original study or data source, not a secondary report or news article about it. If we cannot access the primary source, we note this limitation.
- Assess the evidence level. We determine where the source falls in our hierarchy and adjust the language accordingly. A single case report warrants “has been reported” rather than “has been proven.”
- Cross-reference. Where possible, claims are checked against multiple independent sources. Conflicting evidence is noted rather than suppressed.
- Check for recency. We verify that the source is not superseded by newer research. A 2005 study may still be valid, but if a 2023 meta-analysis reaches a different conclusion, that takes precedence.
How product data is verified
Product information - prices, ingredient lists, concentrations, pH values - requires its own verification approach because this data changes frequently.
- Primary sources. We pull product data from manufacturer websites, official retailer listings, and product packaging. We do not rely on third-party databases alone.
- Data provenance. Every piece of product data in our database is timestamped with when it was collected and from which source. This allows us to track freshness and identify information that needs re-verification.
- Regular re-verification. Product data is re-checked periodically. Prices and availability are checked against live retailer data. Formulation details are verified against manufacturer information.
Data freshness indicators
Product pages display freshness indicators so you can judge how current the data is at a glance:
Data has been recently confirmed against primary sources. Prices, availability, and formulation details are current as of the verification date shown.
Data was accurate at verification but may have changed since. Use as a guide but check the retailer or manufacturer for the latest information.
Data is likely outdated. It is displayed for reference only and should be verified independently before making purchasing decisions.
Limitations we acknowledge
No fact-checking process is perfect. We want to be upfront about the limitations:
- Access to research. Some studies are behind paywalls. When we cannot access the full text, we note this and work from the abstract and any available supplementary data.
- Language bias. We primarily review English-language publications. Relevant research published in other languages may be missed.
- Publication lag. There is always a delay between when research is conducted and when it appears in our content. We aim to incorporate significant new findings as they are identified.
- Product data volatility. Prices and availability can change daily. Our periodic verification means some data may be temporarily outdated. The freshness indicators above help you assess this.
Related policies
For more about how we create and maintain content, see:
- Editorial Policy - our full content creation process
- Our Review Process - how we ensure content accuracy
