Evidence for one airway continues to accumulate. Nasal
allergen challenges increase lower airway
inflammation, and nasal
corticosteroid treatment reduces lower airway
inflammation. Allergic respiratory
inflammation might even spread systemically to involve nonrespiratory organs.
Eosinophilic enteritis and
eosinophilic esophagitis are reported during pollen seasons in patients with
seasonal allergic rhinitis. Chronic hypertrophic
sinusitis (CHS) is found in the majority of patients with
asthma. Like
asthma, the histology of CHS is characterized by epithelial damage, basement membrane thickening, and eosinophilic
inflammation. The damaged epithelium might explain the acute bacterial exacerbations seen in patients with CHS. Studies have extended evidence of the safety and efficacy of the second- and third-generation
antihistamines to younger children and to patients with perennial
rhinitis but continue to show improvement of symptom scores over that seen with placebo of less than 20%. Studies on
antihistamine use in the first trimester in nearly 500 women (65% taking
loratadine) revealed no increase in the complications of pregnancy or congenital anomalies. Positive skin prick test responses to birch in asymptomatic young adults predicted later development of clinical
allergic rhinitis. A dose response was demonstrated for
immunotherapy with cat dander extract. The best results were in subjects receiving a dose containing 15 microg of the major cat
allergen Fel d 1 (equivalent to approximately 2500 bioequivalent
allergen units). Both topical intranasal
immunotherapy and high-dose sublingual immunotherapy have been repeatedly proved to be safe and effective in double-blind, placebo-controlled studies. CD4+CD25+ regulatory T cells secreting
IL-10,
TGF-beta, or both appear important in normal individuals and in patients treated with allergen immunotherapy in maintaining or restoring normal T(H)1/T(H)2 balance and overall suppression of both phenotypes.