Filaggrin is a protein that serves as a fundamental component of healthy human skin. It contributes significantly to the skin’s protective barrier, influencing its ability to retain moisture and defend against external factors. Proper functioning of filaggrin is associated with skin hydration and overall skin well-being.
Understanding Filaggrin and the Skin Barrier
Filaggrin originates from a larger precursor protein called profilaggrin, found in the granular layer of the epidermis, the outermost layer of the skin. During the final stages of skin cell differentiation, profilaggrin is broken down into multiple smaller filaggrin molecules. These molecules then bind to keratin filaments within skin cells, helping to condense them and form a robust, dense protein matrix. This aggregation is important for the structural support and integrity of the stratum corneum.
As skin cells mature and move towards the surface, filaggrin is further broken down into small, water-soluble molecules, including amino acids like pyrrolidone carboxylic acid (PCA) and urocanic acid (UCA). These molecules, along with others such as urea and lactic acid, collectively form the Natural Moisturizing Factor (NMF). NMF components are hygroscopic, attracting and retaining water to keep the stratum corneum hydrated and flexible. This process contributes to the skin’s acidic pH, known as the “acid mantle,” which supports enzyme activity and natural antibacterial properties on the skin surface.
When Filaggrin is Deficient Skin Conditions
Genetic alterations in the FLG gene, which codes for filaggrin, can lead to reduced production or impaired function of this protein. These “loss-of-function” mutations are a known cause of ichthyosis vulgaris, a common skin condition causing dry, scaly skin. It is estimated that up to 2% of the population may have ichthyosis vulgaris, though it is not always diagnosed due to varied severity.
Filaggrin deficiency is also a major factor for atopic dermatitis, or eczema. In individuals with two non-working copies of the FLG gene, there is almost no filaggrin, leading to a much higher risk of eczema. Even those with one non-working copy may have about half the normal amount of filaggrin, increasing their eczema risk. This deficiency compromises the skin barrier, leading to increased transepidermal water loss (TEWL), allowing moisture to escape more easily. A compromised barrier also allows allergens and irritants to penetrate the skin more readily, triggering immune responses and inflammation, contributing to eczema symptoms like dryness, scaling, and itchiness.
Filaggrin’s Link to Other Health Issues
Beyond direct skin conditions, filaggrin deficiency can contribute to a broader pattern of allergic diseases, known as the “atopic march.” This progression often begins with atopic dermatitis in infancy or early childhood, followed by other allergic conditions. Individuals with FLG mutations and atopic dermatitis are more likely to develop allergic rhinitis (hay fever) and asthma.
This progression suggests that a compromised skin barrier, due to filaggrin deficiency, allows environmental allergens to enter the body through the skin. This exposure can sensitize the immune system, leading to IgE antibody production and an allergic response. This makes the body more reactive to these allergens, increasing the risk for other allergic manifestations like food allergies, asthma, and allergic rhinitis. This highlights how skin barrier function can influence systemic immune responses and the development of allergic diseases.
Strategies for Supporting Skin Health
For individuals with filaggrin deficiencies or compromised skin barriers, supporting skin health involves several strategies. Gentle skincare practices are important to avoid further barrier damage. This includes using mild cleansers and avoiding harsh irritants or excessive exfoliation, which can strip the skin’s natural protective elements.
Consistent and adequate moisturization is also beneficial. Moisturizers containing certain ingredients can help fortify the skin barrier and enhance hydration. These include:
Ceramides, which are lipid molecules naturally found in the skin, help rebuild and maintain a strong barrier by filling gaps between skin cells.
Hyaluronic acid, a humectant, attracts and retains water in the skin, contributing to plumpness and hydration.
Emollients, such as shea butter or petrolatum, help smooth the skin and create a protective layer to prevent moisture loss.
Niacinamide (vitamin B3) supports the skin barrier by increasing the production of ceramides and fatty acids.