Secretory IgA (SIgA), an immune marker, is found in saliva in the mouth, throughout the gastrointestinal tract and in the mucus secretions throughout the body. SIgA provides our first line of defence against bacteria, food residue, fungus, parasites and viruses. Deficiency of SigA is the most common immuno-deficiency.

Low levels make us more susceptible to infection and may be a fundamental cause of asthma, autoimmune conditions, coeliac, chronic infections, Crohn’s disease, candidiasis, food intolerance/allergies, autism and other behavioural problems. Very high levels are found in people who have chronic infections and whose immune system is overloaded. Lifestyle and nutritional factors can also influence SIgA levels.