Chinanews.com, Shanghai News, June 29 (Zhang Jian) Qiang Yan, director of the outpatient office and deputy chief physician of Shanghai Dermatology Hospital/Tongji University Dermatology Hospital, recently released a popular science article ""Allergic Stars" Skin Rejuvenate Starts from the Dining Table", the full text is as follows:
Atopic dermatitis (AD) is a common chronic, recurrent, inflammatory, itchy skin condition associated with a genetic allergic diathesis, with an increasing prevalence (Figure 1.). AD patients often have severe itching, which seriously affects the quality of life of patients and their families, and brings heavy economic and psychosocial burdens to patients and their families.
"The people regard food as the sky", and the "Su Wen: Ancient Innocence" contains: "Eat beautifully, let it be served, and enjoy its customs", but AD patients are often required to test for "allergens" and "avoid eating" according to the test report. Blind avoidance not only does not improve allergy symptoms, but also aggravates the risk of allergies and even leads to malnutrition. Therefore, how to scientifically manage the diet of AD "allergic stars", let's start from the dining table and start the journey of skin rejuvenation of "allergic stars".
Figure 1. Global prevalence of food allergies. The prevalence of food allergy-related hospitalizations suggests that the prevalence of food allergies has increased over the past few decades.
Are food allergies the cause of AD?
The causative role of food allergy in AD has been controversial. Studies over the past few decades have shown that compromised skin barrier and skin inflammation are part of the pathogenesis of food allergy. Under certain conditions, such as genetic predisposition, environmental factors, dietary patterns, or early exposure to certain foods, organisms do not develop tolerances that produce abnormal and excessive immune responses to food antigens.
While people of all ages can develop food allergies, children are the most affected. The incidence of food allergy in AD patients is as high as 50.7%, and many children have tried to treat AD by "avoiding food". However, a number of studies have shown that 50%~90% of the presumed "food allergies" are essentially "skin contact allergies", and only 1.4% of the subjects are real "food allergies". Therefore, in the determination of food allergy, we should not only consider the correlation between food arousal and AD skin lesions, but also observe the improvement of clinical symptoms and the recovery of related abnormal immune parameters after food avoidance.
Is it necessary for AD patients to be tested for "food allergies"?
From a diagnostic point of view, it is obviously important to have a food allergy test for AD. However, if an allergy test is performed without a proper reason, especially in babies with AD who have already eaten and tolerated certain foods in the first few years of life, it may lead to a delay in introducing foods into the baby's diet, which in turn increases the risk of some food allergies.
The gold standard for the diagnosis of food allergy is the double-blind placebo-controlled food challenge test (DBPCFC) (Figure 2.), which has high sensitivity and specificity, however, it is time-consuming and carries a high risk of serious reactions. Allergen-specific IgE (sIgE) testing and skin prick testing (SPT) are commonly used diagnostic techniques in clinical practice, but have a high false-positive rate of 90% to 95% negative and < 50% positive predictive value. Therefore, AD food sIgE testing may be more helpful in ruling out food allergies rather than diagnosing them.
Figure 2. Routine diagnostic tests for food allergy: including oral food challenge, skin prick test, and allergen-specific IgE. Other promising tests are in development and are currently limited to the research setting, including basophil activation assays, mast cell activation assays, and bead-based epitope assays.
How to avoid eating in AD patients?
The impact of a reasonable diet on AD is significant. On the one hand, whether to avoid eating depends on the clinical improvement after tabooing. On the other hand, it depends on the improvement of laboratory immune indicators, if the dietary abstinence is carried out and no improvement in the rash is seen, it does not prove food allergy and can be reintroduced. If there is improvement, a food challenge test will help confirm the diagnosis.
Milk: Early and regular introduction of milk formula, even in small amounts, will reduce the risk of milk allergies later in life. But any benefits are weighed against the many known advantages of exclusive breastfeeding. For babies who start using cow's milk formula within a few days of birth, stopping cow's milk formula too early increases the risk of cow's milk allergy.
Breast milk: Breast milk supports the colonization of various microorganisms and promotes the maturation of the newborn's immune system. It is recommended to breastfeed exclusively for at least 4~6 months, starting from 4 months of age, and gradually integrate a more varied diet in addition to breastfeeding to prevent allergic diseases.
Eggs: Early introduction of cooked eggs is effective in reducing the risk of egg allergy in infants with AD, and the introduction of hard-boiled eggs or egg products to all infants around 6 months of age is recommended, but not before 4 months of age.
Peanuts: Early introduction of peanuts and frequent consumption of peanuts can effectively reduce the prevalence of peanut allergy in high-risk infants. Early introduction of peanuts is recommended for low-risk infants at 6 months, including those with no or mild AD. High-risk infants are introduced into peanuts at 4'6 months only when the skin prick test is < 4 mm or if the peanut-specific IgE < 0.35.
Fish & Shellfish: Introducing fish and shellfish within the first year of life can reduce the risk of food allergies, possibly because fish contains high levels of long-chain polyunsaturated fatty acids (LCPUFAs).
Wheat, soybeans, or sesame: It is recommended not to deliberately delay the introduction as early as possible to promote immune tolerance.
Nutrients: there is currently insufficient evidence that vitamin D supplementation can prevent food allergies; Supplementation with specific probiotic bacteria lacks safety regulations, and routine use of probiotics in preterm infants is not recommended. However, studies have also found that various micronutrients in the mother's diet may have an impact on the development of FA, and it is not recommended for pregnant women to exclude common allergens during pregnancy or breastfeeding; Supplementation with Ω-3 LCPUFA, lactobacillus, and bifidobacterium strains in pregnant or lactating mothers reduces AD in children.
Special diets: Diets high in refined carbohydrates and saturated or trans fatty acids have been reported to exacerbate inflammation, with grade I obesity being a positive factor associated with moderate to severe AD. Therefore, mothers adopting a Mediterranean diet, ketogenic diet, low glycemic load diet, diet rich in fruits, vegetables and fish have potential anti-inflammatory and metabolic effects and are being evaluated as stand-alone or adjunctive therapies for dermatological diseases. Conversely, the mother's candy diet, hamburger, fast food Western diet (Figure 4.) Associated with an increased risk of food allergies in susceptible infants. There was no association between vegetarian and vegan diets and the presence or severity of AD.
Figure 3.Association between diet and skin health/disease. Skin health is influenced by the immune system, genetic predisposition, and environmental factors such as UV radiation, smoking, pollution, humidity, and diet. The Western diet has been shown to disrupt the microbiota and cause skin diseases, which can negatively affect skin health.
In short, the course of AD is recurrent and prolonged. In the long course of the disease, although some of the current research results are not supported, the official guidelines emphasize the "causal" relationship between AD and the occurrence of food allergies, i.e., AD is one of the important causes of food allergies, therefore, breastfeeding and early introduction of allergenic foods are encouraged for infants at risk of food allergies, and all infants are advised to have a variety of diets during pregnancy, lactation, and early life, especially the food sources of fruits, vegetables, fish, and vitamin D (Figure 4.).
Figure 4. Early introduction of the mechanism by which food produces immune tolerance. Disruption of the skin barrier and the presence of staphylococcal enterotoxins ("superantigens") lead to Th2 inflammation in AD, loss of tolerance induced by T-regulated cells, and production of food-specific IgE.
Of course, when it comes to "introducing" versus "avoiding" food, any benefits need to be weighed against potential harms, including allergic reactions to food, nutritional problems, and quality of life. "One size fits all" doesn't fit all, and there are many triggers for people with AD, responses to treatment can be different, and patients and families have different expectations when seeing an allergist. However, as a common rule for all AD patients before going for an allergy check-up, a skin management diet diary should be kept first, and skin barrier care should be adhered to, which can not only prevent AD, but also provide protection against allergic sensitization.
Figure 5. "Allergy Star" Diet Diary Form
Remember, scientific diet management is an important step towards health for AD patients, let's start from the dinner table and refuel the skin! (ENDS)
Editor: Zhang Jian