What FLG Means in Your 23andMe Raw Data
FLG in 23andMe raw data is filaggrin. Common loss-of-function variants weaken the skin water barrier and raise eczema odds, but are not a diagnosis.
FLG in your 23andMe raw data is the filaggrin gene. The common variants people check are loss-of-function changes that weaken the skin’s outer water barrier, so carrying one raises your odds of dry skin and eczema. It is not a diagnosis and many carriers never develop eczema.
What does FLG mean in my 23andMe raw data?
FLG codes for profilaggrin, the precursor that gets cut into filaggrin and then into small water-holding molecules. In a raw data file you may see the gene labelled as FLG beside one or more markers. The two most studied variants are R501X and 2282del4, both loss-of-function variants. They produce a shortened protein that cannot do its job.
You might see a genotype such as C/T or T/T for one of these markers, depending on the company’s strand conventions. Do not try to parse the letters unless you know which allele is the risk version. The file is not a clinical report.
If your raw file shows no FLG variant, that is not the same as having a perfect gene. 23andMe tests a fixed set of positions. It does not sequence the whole FLG gene, so a rare private mutation outside the tested positions would not appear.
FLG is a barrier gene, not an eczema verdict. A loss-of-function variant raises the odds, but your environment and other genes decide most of what happens next.
What filaggrin actually does
Filaggrin sits in the granular layer of the epidermis. Its first job is to help keratin fibres bundle together as skin cells flatten and die. Then the protein is broken down into free amino acids. These amino acids are part of the skin’s natural moisturizing factor, which pulls water into the outer layer.
One protein, two jobs. It gives the stratum corneum its physical structure, and its breakdown products act as a humectant. When filaggrin is low, the outer layer loses water faster. Allergens and irritants cross the barrier more easily. That is the mechanism behind the eczema link.
What common FLG variants mean for skin and eczema
A single loss-of-function FLG allele raises the odds of atopic eczema roughly two to three times. Two loss-of-function alleles have a stronger effect. The association is clearest for early-onset eczema and hand eczema that persists.
Carriers often report: - Dry skin that needs moisturizer even in mild weather - Palmar hyperlinearity, where the palms show extra fine lines - Keratosis pilaris, those rough little bumps on upper arms and thighs - Hand eczema that flares with frequent handwashing or wet work
But the same variant can sit in someone with no symptoms. Most large studies find that most carriers do not have a current eczema diagnosis. Genes push in a direction. They rarely decide alone.
Most of the large FLG studies were done in European populations. R501X and 2282del4 are less common in many African and East Asian populations, where other filaggrin variants may matter more.
| Raw data finding | What it usually means | What it does not mean |
|---|---|---|
| No common variant tested | Tested FLG positions are normal | A perfect FLG gene or zero risk |
| One loss-of-function allele | Reduced filaggrin and drier skin; higher eczema odds | A diagnosis or a certainty of eczema |
| Two loss-of-function alleles | Strongest effect; often very dry skin and early eczema | A guarantee of severe disease |
Scroll the table sideways for the rest →
What the result means for risk, not diagnosis.
What it does not mean
A FLG variant is not an eczema diagnosis. It is a baseline skin barrier finding. The common mistake is treating one risk marker as a diagnostic result. Raw DNA files are not that.
A FLG variant does not mean: - You will definitely get eczema - Your eczema, if you have it, is purely genetic - You should avoid all skincare acids or retinoids - Your child will inherit eczema
If you carry one loss-of-function copy, each child has a 50% chance of inheriting that copy. But inheriting it is not the same as developing eczema.
A normal FLG result does not rule out eczema
Most people with atopic eczema do not carry the common FLG loss-of-function variants. Other genes, hard water, soap, sweat, stress and temperature shifts can all weaken the barrier. That is why a negative FLG result is not much of a reassurance. It just removes one well-studied inherited factor.
How to check your own raw data
The free DNA tool at https://healthosx.com/dna reads raw files from 23andMe, AncestryDNA, MyHeritage and whole-genome VCFs in the browser. The trait report includes the FLG finding. For the trait and medication response part, the file does not leave your device.
If your file contains an FLG marker, the report will show the gene with a headline about how well your skin holds water in. If you do not see it, the tested positions only are your answer.
The download steps for 23andMe, on the page itself.
The short version: what is worth acting on, first.
FLG is one of the few raw DNA findings that connects cleanly to a visible physical trait. Read it as a background risk, not a verdict. If your skin is currently fine, a carrier finding changes little about your day.
New to raw DNA files? Start with the full guide: How to Download & Analyze Your 23andMe Raw Data Free
Written by
HealthOS Research