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‐anlagonists will become a routine therapeutic procedure in allergy therapy.