Unpacking the hygiene hypothesis: raw milk proteins may protect against allergy

The allergy-protective effects of exposure to dirt and ‘germs’ during childhood is a key part of the hygiene hypothesis that aims to explain why allergies are now more prevalent than ever. Several past studies have shown children who grow up on farms and drink untreated milk are less likely to suffer from allergies and asthma than city-dwellers, yet the mechanisms behind this have not been fully explored.

A recent study conducted in Vienna has shown that the beta-lactoglobulin protein in raw milk is a key molecule that can protect against the development of immunoglobulins E (IgE) which are responsible for symptoms in people with allergies.

Beta-lactoglobulin is the most abundant whey protein in cow’s milk and one of the major milk allergens. It is known for its ability to bind a wide range of other molecules, or ligands.

In laboratory-based studies, the research team showed that when it is carrying its natural ligands – such as plant pigments from green grass – beta-lactoglobulin prevents allergies. Conversely, when it is without its natural ligands, the protein behaves like an allergen.

The anti-allergenic properties of natural beta-lactoglobulin can be explained by the fact that this protein specifically delivers its ligands to the immune cells, thereby preventing inflammation. The natural ligands also prevent IgE antibodies from ‘docking’ onto beta-lactoglobulin protein, so that it should be better tolerated by children with milk allergy.

The study authors say circumstances that could lead to a loss or lack of the allergy-protective natural ligands binding to the beta-lactoglobulin proteins include industrial milk processing or poor quality animal feed.

Reference: Roth-Walter et al. The Journal of Allergy and Clinical Immunology 2020. doi.org/10.1016/j.jaci.2020.05.023.