Allergy affects approximately 25% of the UK population at some time of their lives, with children representing up to 50% of those affected. Numbers of sufferers are increasing each year. Reduced exposure to microbial allergens in early childhood (the hygiene hypothesis) has been proposed as one factor to explain this.
The allergic response results from an imbalance of Th1:Th2 cells, causing an overreaction to normally harmless substances resulting in symptoms including; rhinitis, eczema, and asthma. An aberrant intestinal microbiota has been shown for infants with allergies, with higher numbers of clostridia, fewer bifidobacteria and with species more typical of those in adults.
There has been probiotic research in this area, with many studies focussing on modulation of the immune system in early childhood. Studies have been conducted with L.casei Shirota, investigating effects on adults with allergic rhinitis, mainly investigating downregulation of the immune response.
Study: Allergy - rhinitis
Effect on allergic rhinitis - Ivory et al. (2008) Clinical & Experimental Allergy 38(8):1282-1289
Method: This double-blind, placebo-controlled pilot study, included twenty healthy seasonal allergic rhinitis (SAR) sufferers, who consumed a daily probiotic drink containing L. casei Shirota (6.5 x 109 live cells of LcS) or a placebo drink for five months. Fasting blood samples were taken pre-, peak- and post- grass pollen season for analysis of total plasma IgE, and levels of IgE and IgG specific for grass pollen antigens (GX1 and GX2). In addition, cytokine expression was analysed in the presence or absence of the same grass pollen antigens.
Results: Oral administration of LcS resulted in modification of the allergen-specific response in SAR. Significantly lower levels of allergen-induced cytokines (IL-5, IL-6 and IFN-γ) were found in the probiotic group compared with the control group (P <0.05). In addition, levels of specific IgG increased and IgE decreased in the LcS.
It is important to note that benefits associated with immune changes can only be properly determined by studies that also look at clinical changes. One study with L. casei Shirota investigated its effect on symptoms of people with allergic rhinitis induced by Japanese cedar pollen. No benefit was shown overall but a sub-group of people with moderate to severe nasal symptom scores did show a tendency for alleviation of symptoms that was associated with the L. casei Shirota intervention (Tamura et al. 2007).