The prevalence of fungal allergy is increasing and it is becoming an important clinical problem. The source of allergens might be air, food, drugs and distant sites of fungal inflammation. Allergy to moulds usually coexists with other allergies, hence the important role of nasal challenge. The assessment of the provocation should include the late phase, which might be the only reaction to mould allergen. A valuable measurement confirming the result is increase in eosinophil number in the nasal fluid, found in the majority of patients.