IGHE and allergic disease: BM21, the vaccine for grass pollen contains non-IgE-reactive peptides derived from the IgE-binding sites of the grass pollen allergens and covalently linked to Pre S from hepatitis B virus, a viral protein carrier that provides carrier-specific T cell help was tested in clinical trials [189–191] and the phase 2b multi-centred, double-blinded, placebo-controlled study reported that BM21 can relieve allergy symptoms and is well tolerated without severe adverse effects [194,195].