A nebulizer for a fluid, particularly for medical aerosol treatment is proposed. To allow easier operation and confer improved operational reliability a sealed container holding the fluid is already arranged in the nebulizer when it is supplied and the nebulizer is constructed so that the container is opened inside the nebulizer before or during the first use of the nebulizer. Alternatively, or in addition, the nebulizer is constructed so that the container cannot be replaced, and in particular, cannot be removed.
