Type I allergy represents a hypersensitivity occurring in almost 20% of the population that is based on the recognition of innocuous airborn antigens (pollen, mite, mould and pet allergens) by specific immunoglobulin E. Allergic symptoms (e.g. allergic rhinitis, conjunctivitis, asthma) are caused by the release of biological mediators from effector-cells after allergen-induced crosslink of receptor-bound IgE. Here we discuss strategies to obtain recombinant allergen-specific antibody fragment...