H1- and H2-antagonists in allergic and pseudoallergic diseases.
Although known for more than 80 years, histamine still remains a fascinating substance for allergy research. Histamine antagonists have been in clinical use since 1942. The classical H1-antagonists with sedative side-effects have been more or less replaced by newer non-sedating H1-antagonists; the role of H2-receptors in allergic diseases is still controversial. There, are however, increasing reports of beneficial effects of H2-antagonists, mostly in combination with H1-antagonists, in a variety of allergic and pseudoallergic conditions such as chronic urticaria, anaphylactoid reactions due to colloid volume substitutes, opioid analgesics and radiographic contrast media. The combined use of H1- and H2-antagonists might not only act as specific histamine antagonism but exert a mast cell stabilizing effect, as demonstrated in animal experiments and some clinical studies. Future research will show whether the combined use of H1- and H2-antagonists will become a routine therapeutic procedure in allergy therapy.