Allergic Diseases Especially Atopic Dermatitis Biology Essay



Allergic diseases, especially atopic dermatitis which is characterized by pruritus, eczematous lesions, xerosis (dry skin), and lichenification (thickening of the skin and an increase in skin markings), are prevalent in many developed countries and there seems to be an increasing trend. To combat the rising prevalence of allergy, there is still a need to analyze the underlying mechanisms and to develop concepts that address primary prevention (Kopp et. al). An altered microbial exposure in the gastrointestinal tract may be partly responsible for the increase of allergic diseases in populations with a western life style. The recognition of the importance of intestinal flora has led to the development of strategies aimed at manipulating bacterial colonization in formula fed infants, including the use of prebiotics and probiotics (Osborn et. al). Probiotics are live bacteria that colonize the gastrointestinal tract and provide a health benefit to the host by improving its intestinal microbial balance. The importance of the microbiota composition may culminate in early infancy when maturation of the gut barrier functions and immune development occurs. Probiotic intervention in the neonatal period has attracted scientific interest after recent demonstrations showing that specific strains reduce the symptoms and risk of allergic and infectious disease. The suggested mechanisms whereby probiotics exert these effects are composed of balancing effect on gut microbiota, maintenance of gut barrier functions and control of inflammatory response (Rinne et. al). Probiotics have been demonstrated to have anti-inflammatory properties associated with changes in cytokine expression that could potentially facilitate Th1 cell immune response, which could inhibit the development of allergic Th2 cell response and allergic IgE antibody production. Several randomized studies have now demonstrated efficacy from the use of probiotics in infants with active eczema. Prebiotics are non-digestible food components that beneficially affect the host by selectively stimulating the growth or activity of bacteria in the colon. They can be added to infant formula. In infants, studies have demonstrated significant increases in fecal bifidobacteria in response to formula supplementation with oligosaccharides. Probiotics may be modified by the addition of a prebiotic to infant feeds.

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Genetic susceptibility plays a significant role in the development of atopic dermatitis. Although less than half of those who develop childhood allergic disease have a first degree relative with a history of allergy, the risk of development of allergic diseases increases substantially with a positive family history of allergy. Approximately 10% of children without an allergic first degree relative develop allergic disease compared to 20-30% with an allergic first degree relative and 40-50% with two affected relatives. The manifestations of allergic disease are age dependent. Infants commonly present with symptoms and signs of atopic eczema, gastrointestinal symptoms and recurrent wheezing. Asthma and rhinoconjunctivitis become prevalent in later childhood. Sensitization to allergens tends to follow a characteristic pattern, with sensitization to food allergens in the first two to three years of life, followed by indoor allergens (ex. House dust mite and pets) and subsequently outdoor allergens (ex. Rye and timothy grass) (Osborn et. al).

Improved hygiene, the increased use of antimicrobial medication, the consumption of sterile food, and reduced family size resulting in lower rates of infection during childhood have reduced early contact to microbes. This may interfere with the development of the child’s immune system, which tends to be directed toward a T-helper 2 (Th2) phenotype in infants, whereas postnatal maturation is associated with gradual inhibition of Th2 and increasing Th1 affinity. Experimental and epidemiologic data show strong evidence for the hypothesis that early microbial exposure is a critical feature for Th1-skewed immune response in healthy children during the postnatal period. Less exposure to microbial agents at an early age would, therefore, result in reduced activation of the immune system and subsequent polarization toward a Th2 phenotype. Therefore, the idea of modulating the intestinal flora has really caught on and is gaining in popularity. This concept is supported by epidemiologic data, which show that children with allergy have a different intestinal flora from healthy children with higher levels of clostridia and lower levels of bifidobacteria (Kopp et al).

Intestinal colonization during and immediately following birth represents the first contact for the newborn with microbes. The gradual colonization depends on the mother’s microbiota, mode of delivery and environment. The genus Bifidobacterium constitutes the predominant group in the fecal microbiota of healthy infants, commonly consisting of the species Bifidobacterium infantis, B. longum, and B. breve. Bifidobacterium longum was the species most commonly found in the mothers. Breast-feeding promotes the growth of the microbial strains already present in the gut of the infant, specific changes in the transfer and initial establishment of bifidobacteria in neonates take place as consequence of the consumption of L. rhamnosus GG by the mothers (Gueimonde et. al).

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Controversy exists regarding the preventive effect of probiotics on the development of eczema or atopic dermatitis. Some RCT studies show that administration of probiotics from the prenatal period through to the first months of life may lead to reduced incidence of eczema and may also influence the development of infants’ Bifidobacterium microbiota (Osborn et. al). But other RCT studies showed that supplementation with Lactobacillus GG (LGG) during pregnancy and early infancy neither reduced the incidence of atopic dermatitis nor altered the severity of atopic dermatitis in affected children. One study showed that prenatal and postnatal supplementation with a mixture of B. bifidum BGN4, B. lactis AD011, and L. acidophilus AD031 is an effective approach in preventing the development of eczema in infants at high risk of allergy during the first year of life. In this study, we are trying to determine if supplementation of mother during late pregnancy and early infancy with single strain of probiotic would lower the incidence of atopic dermatitis for infants that are at high risk of allergy or food hypersensitivity.

Null hypothesis

Supplementation of mother during late pregnancy and early infancy with a single probiotic strain (LGG) would not affect the incidence of atopic dermatitis for infants that are at high risk of allergy or food hypersensitivity

Research hypothesis/question

Supplementation of mother during late pregnancy and early infancy with a single probiotic strain (LGG) would lower the incidence of atopic dermatitis for infants that are at high risk of allergy or food hypersensitivity.


Infants were either breast-fed or formula fed during the first 6 months

Participants are compliant with their probiotic supplements


Single probiotic strain use: Lactobacillus rhamnosus GG (LGG)

Time frame: 36 weeks of gestation until 6 months infancy

Dosage of LGG: 1.8 X 1010 colony-forming units

Population size: 100 pregnant women and their newborn infants


The exact cause of atopic dermatitis is unclear

The ideal dosage of LGG is not certain

The best probiotic strain is unknown

Operational definition

Infants at risk for Atopic Dermatitis:

Infants who have other allergic disease such as food allergy, asthma, etc

Infants who have one or more first degree relatives that have allergic disease