The invention relates to a method suitable for administering protein therapeutic molecules orally, sublingually, topically, intravenously, subcutaneously, nasally, vaginally, rectally or by inhalation so as to avoid inactivation, by using VHH polypeptides derived from Camelidae antibodies. The invention further relates to the said therapeutic molecules. The invention further relates to a method for delivering therapeutic molecules to the interior of cells. The invention further relates to anti-IgE therapeutic molecules.