Abstract
This review discusses available evidence on the mechanisms of action of bacterial lysates, and the clinical effects of their sublingual administration. Bacterial lysates act through many immunological effects, including dendritic cell activation, modification of circulating lymphocyte subsets and antibody production. The production of salivary IgA was repeatedly shown to be induced by the sublingual administration of a prototype bacterial lysate containing soluble and corpuscular antigens. Bacterial lysates are a useful tool for the prevention of recurrent respiratory tract infections. Sublingual administration should be the preferred option.