Eosinophils, specific hyperreactivity and occurrence of late phase reaction in allergic rhinitis

Eosinophil infiltration may be considered characteristic of nasal allergic inflammation. However, a mild inflammatory infiltrate may be present in asymptomatic subjects exposed to specific allergen.

We investigated the relationship between inflammation, specific hyperreactivity and clinical late phase reactions in allergic subjects using the ASNC model.

Sixty allergic subjects (aged from 18 to 47 years) were enrolled among those sensitized to pollens (n=20) and those to house dust mite with (n=20) or without (n=20) known clinical nasal LPR. All subjects were asymptomatic. TNSS and eosinophil number were assessed at baseline, 30 min (early phase) and 6 hours (late phase) after ASNC.

Eosinophil number was higher in LPR+ rhinitics than in other groups, at baseline and during the early and late phase (p<0.001). ATD was lower in LPR+ rhinitics than in other groups (p<0.001). In LPR+ rhinitics, at baseline there was a significant correlation between eosinophils and ATD (r=0.56, p=0.009). After allergen challenge, TNSS was significantly higher in LPR+ rhinitics than in other groups, both during early and late phase (p<0.001 for all comparisons).

In house dust mite sensitised subjects, LPR occurrence after allergen challenge is associated with higher inflammation and lower ATD at baseline. Therefore, in house dust mite allergy minimal persistent inflammation without symptoms can drive different clinical responses to allergen challenge.