Allergies occur in many different forms and are characterized by an excessive response of the body to external stimuli. These stimuli can enter the body in various ways, for instance via the skin, respiratory tract or the mouth. Commonly known allergy triggers, known as allergens, are house dust mites (or rather their faeces), grass pollen and plant seeds (hay fever) and foods such as peanuts and shellfish. The cause of allergies can be attributed to different factors, including genetic factors, immune system abnormalities, environmental factors and a poorly developed skin barrier function.
In an allergic reaction, the immune system produces IgE antibodies against the allergen, which triggers the production of histamine. Histamine affects the eyes, throat, nose, gut, skin or lungs, producing the characteristics that we recognize as an allergic reaction.
The degree to which the body responds to an antigen depends on the balance between types of T helper (Th) cells. In case of allergies, this balance will have shifted in favour of Th2 cells.1 The subpopulation of Th2 cells is associated with the production of IgE antibodies and atopic disease. Th1 cells are the antagonists of this response. It is known that during pregnancy a shift towards Th2 occurs to prevent the mother’s immune system from rejecting the foetus. This imbalance will persist in the newborn baby for several months.2
The development of the correct balance requires genetic factors, but also external influences. Insufficient stimuli can disrupt this development, resulting in the onset of atopic allergy.3 This will initially present as atopic eczema in babies and young children. A fair number of such children will develop other forms of allergy later in life, such as asthma and hay fever. This process is also referred to as the “allergic march”.5
Microbiota management and allergy
The development of the immune system and that of the microbiota are intimately linked. The microbiota therefore plays a vital role in establishing a correct Th1/Th2 balance. According to the hygiene hypothesis, modern hygiene practices prevent children from being exposed to bacteria to stimulate their immune system.5 This affects the Th1/Th2 balance, meaning children will be more susceptible to developing atopic conditions. Children who are delivered by Caesarean section are also less exposed to bacteria. As a result, development of their microbiota is different to that of other children born by natural delivery. Statistically, these children are more likely to develop some form of allergy.6 7 Early interventions to ensure adequate development of the immune system are therefore needed to minimize the likelihood of allergies. Studies show it is possible to ensure that children born by Caesarian section receive sufficient bacteria through exposure to the mother’s vaginal fluids to allow a healthy gut microbiota to develop.8
Probiotics and allergy
There is a growing body of evidence to support the idea of probiotics aiding the development of a healthy immune system, thereby preventing allergies.9 Especially prenatal use of probiotics by the mother, followed by probiotics for the newborn baby has proved to be an effective method for preventing allergies.10 As shown in a number of different studies, this effect is especially prominent when a multispecies probiotic is used. In these studies, a mix of B. bifidum, B. lactis and Lb. acidophilus11, or B. bifidum, B. lactis and L. lactis12 was used.
A great deal of research has also been devoted to the role of probiotics in the management of existing eczema13 14 15 16 and hay fever symptoms17 18 but with less consistent results. This is related to the high degree of heterogeneity in study design, parameters measured, dosages and the strains used. We know that the beneficial effects of probiotics are strain-specific. Probiotics can, in fact, relieve hay fever symptoms and thereby improve quality of life.18
Because of the major impact an allergy can have on a person’s private life and their high prevalence, allergies also place a significant social burden on present-day Western societies.19 20 Allergies also represent a considerable burden on healthcare provision and healthcare costs as well, while allergy sufferers experience their condition as having an adverse effect on their quality of life. All of this demonstrates the impact of allergies and the need to reduce the likelihood of allergies in the earliest possible stage. Specifically, selected probiotics offer a safe and simple method to achieve this aim.
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