Nasal challenge with allergen or mediators is a useful model to understand the pathophysiology of allergic rhinitis. Some mechanisms have thereby been clearly clarified. Different methods have been proposed to mimic the natural allergen exposure and to measure the clinical and biological responses. Nasal challenges can also be used in clinical practice, mainly when there is a discrepancy between results of skin tests and in vitro or when occupational allergens are involved. Nasal challenges are also valuable to assess the efficacy of specific immunotherapy or some drugs.