Why Do Babies Have Atopic Dermatitis?
Allergic reactions occur when the body’s immune system overreacts to harmless substances. Atopic dermatitis is a common allergic skin disease caused by the body producing excessive IgE antibodies and triggering inflammatory responses after exposure to specific allergens (sensitizers).
Allergens can be divided into food allergens and airborne allergens. Food allergens cause gastrointestinal and skin symptoms such as atopic dermatitis and hives, while airborne allergens often lead to respiratory issues like rhinitis and asthma.
Airborne Allergens
House Dust Mites
The most common airborne allergen in Taiwan is house dust mites. Dust mites are tiny arthropods that thrive in warm, humid environments, making Taiwan’s subtropical climate ideal for their growth. Household dust contains large quantities of dust mites, which can easily trigger allergic reactions in atopic dermatitis patients when their skin is injured.
Mold
Taiwan’s humid climate also facilitates mold growth, accounting for around 20% of airborne allergens.
Animal Dander
Animal dander is another common allergen. In Taiwan, dog dander allergies are more prevalent than cat dander allergies, which are more common in the United States. However, as more people keep cats as pets, cat dander allergies may increase. Cats’ sebaceous glands secrete highly allergenic proteins that can cause allergic reactions after prolonged exposure.
Food Allergens
Shellfish
In Taiwan, shellfish such as shrimp, crabs, and oysters are the most common food allergens, accounting for about half of all food allergies.
Certain Fruits
Some tropical fruits, such as mangoes, kiwis, and strawberries, are also common food allergens in Taiwan, with mangoes being particularly prevalent in the southern regions.
While blood tests can detect food-specific IgE antibodies and assess allergy risks, confirming an actual food allergy requires observing the patient’s reaction after consuming the suspected food. Some food allergens may become more allergenic when cooked or spoiled, so an initial negative blood test does not completely rule out the possibility of an allergy.
The Impact of Modern Dietary Additives
In recent years, some chemicals added to food or animal feed, such as plasticizers, hormones, and antibiotics, have been found to promote the differentiation of type 2 helper T cells, thereby increasing the risk of allergic reactions.
Plasticizers
Research has shown that plasticizers not only increase the incidence of allergic diseases but also promote the development of type 2 helper T cells in vitro experiments.
Hormones and Antibiotics
Growth hormones are commonly added to livestock feed to increase yield, but these hormones can also increase the activity of type 2 helper T cells. Meanwhile, excessive use of antibiotics can disrupt the gut microbiome, impairing the development of a normal immune system and increasing the risk of allergies.
Managing Allergies During Pregnancy
Atopic dermatitis patients typically have much higher IgE antibody levels than asthma patients, and their allergens are highly diverse, including both food and airborne allergens. Common food allergens include milk, eggs, seafood, and certain fruits.
The Influence of Maternal Allergies
One possible explanation is that during pregnancy, the mother’s allergic constitution causes specific molecules to cross the placenta and affect the developing immune cells of the fetus. Therefore, expectant mothers should control their allergic reactions and avoid foods that trigger symptoms, but they can consume nutritious foods that do not cause allergies in moderation.
The Intrauterine Environment
Another possibility is that these infants with atopic dermatitis are genetically or constitutionally more sensitive to type 2 helper T cell stimulation, leading to immune dysregulation and excessive IgE antibody production within the uterus. However, these hypotheses currently lack evidence and require further research to clarify the underlying mechanisms.
The “Golden Period” for Improving Atopic Dermatitis
For newborns, the first allergens they encounter are food allergens. However, as children grow older and start scratching, skin injuries make them more susceptible to airborne allergens, exacerbating their allergic condition.
Therefore, in treating atopic dermatitis, it is crucial to prevent the patient’s allergens from transitioning from food allergens to airborne allergens, as the latter are much harder to control. Experts suggest that the golden period for treating atopic dermatitis is within the first 1.5 years of life, following the principle of “stop eating before age 1, stop scratching after age 1,” which significantly increases the chances of complete remission.
The reason is that when food allergens are ingested, the body develops a certain level of tolerance mechanisms to regulate the allergic response. However, airborne allergens like dust mites and bacterial endotoxins cannot be ingested in large quantities, so no oral tolerance mechanism can be established. Once they become allergens, a vicious cycle ensues, making it difficult to achieve a complete cure.
Allergy Trivia
Why Do Infants Who Haven’t Consumed Adult Foods Still Have Food Allergies?
Although infants have not been exposed to adult diets, the most common food allergens are milk and eggs because these are the first foreign proteins they encounter. Therefore, it is recommended to exclusively breastfeed after birth, and only gradually introduce complementary foods such as cow’s milk or egg yolks around 4.5 months of age. If breastfeeding is not possible and severe allergic symptoms persist, partially hydrolyzed, hypoallergenic infant formulas may be considered.
Can Probiotic Supplementation Help Prevent Allergies?
In recent years, many studies have focused on the effects of probiotic supplementation on immune cell activation and the potential reduction of allergic reactions. Large-scale studies have suggested that probiotics can improve the symptoms of atopic dermatitis.
However, the results of different clinical trials on the preventive effects of probiotics on asthma and allergic rhinitis have been inconsistent. The most likely reason is thought to be related to the specific probiotic strains used, as different strains may have varying effects on modulating the immune response. More clinical research is needed to address this issue conclusively.
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