Eczema, a chronic inflammatory skin condition, is prevalent worldwide, affecting millions. Its prevalence varies across age groups, with a notable occurrence in infants and young children, where it often manifests as atopic dermatitis. Studies indicate that approximately 20% of children and 10% of adults globally experience eczema. The condition's prevalence has been on the rise in recent decades, with environmental factors and genetic predispositions contributing to its development.

Beyond traditional approaches, the emerging understanding of the gut-skin connection has added a new dimension to eczema management. Recognizing the interplay between gut health and skin conditions has led to increased exploration of dietary interventions, offering individuals with eczema additional strategies to enhance their overall well-being and quality of life. (17, 21)

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What Is Eczema?

Eczema, also known as atopic dermatitis (AD), is a chronic inflammatory skin condition characterized by red, itchy rashes. AD symptoms can appear anywhere on the body and include:

• Dry, cracked skin
• Itching that can lead to raw, sensitive skin from scratching
• Rash on swollen skin that varies in color (depending on skin color)
• Small, raised bumps
• Oozing and crusting
• Thickened skin
• Darkening of skin around the eyes

Eczema often presents in children before age five and may continue into adolescence and adulthood. AD often cooccurs with allergic rhinitis (hay fever) and asthma – collectively called the allergic triad. In a cross-sectional study including 2,270 children with AD, nearly three-quarters (71.3%) of participants reported at least one additional form of allergic disease (i.e., allergic rhinitis or asthma) in addition to eczema. Over one-third of participants (38%) reported symptoms of all three allergic triad conditions. 

AD is the most prevalent of seven eczema subtypes, also including contact dermatitis, dyshidrotic eczema, hand eczema, neurodermatitis, nummular eczema, and stasis dermatitis. Each type of eczema has a unique presentation, but it is possible to have multiple types simultaneously.  

Traditional treatment approaches for eczema primarily involve managing symptoms and preventing flare-ups. Emollients and moisturizers help maintain skin hydration, while topical corticosteroids are commonly prescribed to reduce inflammation. Additionally, antihistamines may alleviate itching. Identifying and avoiding triggers, such as certain allergens or irritants, plays a crucial role in managing eczema. While these approaches relieve symptoms for many individuals, ongoing research explores newer therapeutic options, including immunomodulators and targeted biologic agents, to address the underlying immune system dysfunction associated with eczema. (3)

What Causes Eczema?

The causes of eczema are multifaceted, involving a complex interplay of genetic, environmental, and immune system factors. Genetic predisposition is a significant contributor, with individuals having a family history of allergic conditions being more susceptible. Children who have two parents with eczema have a 50% chance of developing eczema themselves. Certain gene variations affect the skin's barrier function and immune responses, increasing the risk of eczema. A mutation in the filaggrin gene is associated with eczema. This mutation compromises the production of filaggrin, a protein essential for maintaining the skin's protective barrier. Reduced filaggrin levels result in a weakened skin barrier, allowing moisture loss and increased penetration of irritants and allergens, contributing to skin inflammation and the characteristic symptoms of eczema.

Beta-defensins are antimicrobial peptides, part of the innate immune system, with a crucial role in the skin's defense against infections. In eczema, evidence suggests a dysregulation in the expression and function of beta-defensins. This dysregulation may contribute to the pathogenesis of eczema by disrupting the skin's natural defense mechanisms. Altered beta-defensin levels can compromise the skin's ability to combat pathogens, potentially leading to an increased susceptibility to infections, especially Staphylococcus aureus and Candida albicans, and contributing to the inflammatory responses observed in eczema. (4) 

Environmental and emotional factors are also implicated in eczema's pathogenesis. Exposure to allergens, irritants, or microbes can trigger an inflammatory response in the skin, contributing to eczema development. Common triggers include airborne allergens, such as pollen or pet dander, and contact irritants, like harsh soaps or chemicals. Additionally, climatic conditions, such as extreme temperatures or low humidity, can exacerbate symptoms. (16) 

Central to eczema pathology is the dysregulation of the immune response. In individuals with eczema, the immune system overreacts to environmental triggers, releasing inflammatory substances that lead to skin inflammation and itching. This chronic inflammation disrupts the skin barrier, making it more susceptible to irritants and allergens, creating a cycle of exacerbation. (41) 

The Gut-Skin Axis

The gut-skin axis is a bidirectional communication system between the gastrointestinal tract and the skin, emphasizing the interplay between gut health and skin conditions, such as eczema. The gut microbiome, a diverse community of microorganisms residing in the gastrointestinal tract, modulates local and systemic immune responses, aids digestion, and synthesizes nutrients that fortify skin barrier integrity. 

Gut health's impact on eczema relates to the progression from gut dysbiosis to skin dysbiosis, which involves a cascade of interconnected events. Initially, disruptions in the gut microbiome, influenced by factors such as diet, antibiotic use, and stress, lead to an imbalance in microbial composition – a state known as gut dysbiosis. This dysbiosis triggers increased intestinal permeability, or "leaky gut," allowing the translocation of bacteria and other inflammatory agents into the bloodstream. The systemic immune response activated in the gut can manifest in the skin, contributing to skin dysbiosis and inflammation. Impairment of the skin barrier combined with altered skin microbiota increases the likelihood of external allergens, irritants, and pathogens passing into the skin, further perpetuating chronic skin inflammation. (25) 

Distinct dysbiotic patterns have been noted in patients with eczema, including lower levels of beneficial Bifidobacteria, Baceteriodetes, and Bacteroides in conjunction with higher levels of pathogenic Clostrioides difficile, Escherichia coli, and Staphylococcus aureus (39). Multiple gastrointestinal comorbidities are also common in patients with AD, including adverse food reactions, eosinophilic esophagitis, Crohn's disease, celiac disease, irritable bowel syndrome (IBS), and gastroesophageal reflux disease (GERD).

Dietary Factors Affecting Eczema

Food allergies affect 30% of children suffering from moderate-to-severe eczema, and clinical studies have documented the collective prevalence of food allergy in AD as high as 80%. Three-quarters of food-induced AD flares have been attributed to exposure to dairy, egg, wheat, soy, and peanut. 

Nosrati et al. conducted a cross-sectional study that surveyed 169 patients with AD using a 61-question survey about dietary modifications, perceptions, and clinical outcomes. Of those who experimented with dietary elimination, the best improvements in eczema were reported with the exclusion of white flour products, gluten, and nightshades. For those who added food items into their diets, the best improvements in skin were noted with the incorporation of vegetables, organic foods, and fish oil. 

Research also suggests that AD may cause food sensitization. In population-based studies, the likelihood of food sensitization is six times higher in patients with AD versus healthy controls at three months of age. There is evidence to suggest that AD precedes the development of food sensitization and that there is a positive correlation between the severity and chronicity of AD and food allergy. These findings suggest that even if food allergies and sensitivities are not initially responsible for the development of eczema, they can develop later. This may be one of the mechanisms behind the increased prevalence of gastrointestinal comorbidities in patients with AD. (38) 

Implementing Dietary Changes for Eczema Management

A 2022 systematic review and meta-analysis found that eliminating trigger foods may alleviate some AD symptoms, such as itching and sleeplessness, slightly. Based on the complex and intertwined web of food sensitization, inflammation, gut health, and eczema, it is reasonable to implement an elimination diet when food-exacerbated eczema is suspected. Food-exacerbated eczema should begin to improve during a three-to-four-week trial elimination period. The most common dietary culprits of eczema should be eliminated during this time: gluten, dairy, egg, soy, peanut, and nightshades. If food elimination does not result in symptom improvement, foods should be reintroduced back into the diet to prevent potential consequences of long-term dietary restriction, and alternative eczema triggers should be pursued. 

For patients with food-exacerbated eczema, the duration of an elimination diet varies, averaging around four weeks. Following this period, a systematic reintroduction phase is crucial to identify specific foods triggering adverse reactions. This gold-standard approach involves reintroducing eliminated foods one at a time, allowing several days between reintroductions to monitor potential symptoms, to diagnose food sensitivities contributing to eczema accurately. A diet-symptom diary is a helpful method to connect symptoms with food triggers. Reintroduced foods that do not exacerbate eczema can be reincorporated into the diet, while foods that worsen eczema symptoms should be avoided. (14) 

There are also plenty of dietary modifications that can help treat eczema that do not involve the elimination of foods from the diet. As mentioned above, patients with AD self-report improvements in eczema by incorporating vegetables and fish into their diets. These foods are rich in fiber, polyphenols, and omega-3 fatty acids, which are anti-inflammatory, support digestive function, and nourish the gut microbiome. (28) 

Probiotics, Prebiotics, and Eczema

Prebiotics are non-digestible fibers and compounds that fuel beneficial bacteria in the gut, promoting their growth and activity. These substances are not broken down by the digestive process, reaching the colon intact, where they selectively nourish beneficial bacteria. Common sources of prebiotics include bananas, onions, garlic, leeks, asparagus, Jerusalem artichokes, and whole grains. Prebiotics enhance bacterial production of short-chain fatty acids (SCFAs), which have anti-inflammatory effects.

Probiotics are live microorganisms that confer health benefits when consumed in adequate amounts. These microorganisms contribute to a balanced gut microbiome and modulate the immune system to reduce inflammation. Probiotics can be obtained from various dietary sources, such as yogurt, kefir, sauerkraut, kimchi, and miso, or through probiotic supplements. The severity of eczema inversely correlates with intestinal microbiota diversity and butyrate-producing bacteria. Butyrate is one type of SCFA.

There is conflicting evidence on whether oral prebiotics and probiotics help treat AD. In a 2019 systematic review including 44 studies, nearly half of the studies showed that probiotic use positively affected AD severity. The remaining half did not show any effect of probiotics on AD severity. These conflicting results may be due to differences in the doses, strains, and courses of probiotics used in clinical interventions, highlighting the importance of tailoring probiotic and prebiotic therapy to individual needs. A 2023 systematic review indicates that topical probiotic therapy exhibits promise in alleviating symptoms associated with eczema, suggesting an alternative avenue for probiotic intervention for those who do not respond to oral administration.

Challenges and Considerations in Dietary Management

Identifying food triggers in patients with eczema poses challenges due to the complexity and variability of individual responses. Eczema triggers can be elusive, often involving a combination of genetic predispositions, environmental factors, and dietary influences. Symptoms may not manifest immediately after consuming trigger foods, making it challenging to establish clear cause-and-effect relationships. Furthermore, eczema triggers can differ among individuals, complicating the identification process. Functional medicine testing can help identify adverse food reactions and customize a starting point for an elimination diet. Blood tests that measure IgE, IgA, and IgG immune proteins can assist in diagnosing food allergies and sensitivities. The following food panels are commonly ordered through Rupa Health:

• 50 Food Panel: IgE by US BioTek 
• 96 IgA Food Sensitivity Panel by Alletess Medical Laboratory
• 96 IgG Food Sensitivity Panel by Alletess Medical Laboratory

Patients on long-term restricted diets are at a higher risk of nutritional deficiencies, especially children. Children with multiple food allergies have a lower intake of total calories, micronutrients, and macronutrients and are reported to be smaller in height and weight than children without. (19) This dilemma underscores the importance of careful dietary planning and regular monitoring by healthcare professionals, such as registered dietitians, who can provide personalized guidance to mitigate the risk of nutritional deficiencies while effectively managing eczema in children through dietary interventions. Comprehensive nutritional assessments, such as Genova Diagnostics' NutrEval test, enable healthcare professionals to tailor precise dietary and supplemental treatment plans that effectively address and prevent nutritional inadequacies in individuals eating restricted diets.

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Conclusion

The connection between diet, gut health, and eczema management underscores the potential impact of dietary interventions in alleviating symptoms. Evidence suggests that addressing gut health through personalized nutritional strategies, including elimination diets and the incorporation of gut-healing foods, may contribute to the overall management of eczema. Individuals with eczema are encouraged to explore these approaches as part of a comprehensive management plan. Optimizing eczema outcomes through diet should be done under the care of healthcare professionals, such as registered dietitians or functional medicine practitioners. Collaboration with experts helps identify specific food triggers through functional medicine testing and ensures that dietary changes are implemented safely and effectively.