Asthma is a variable disease, and can be exacerbated by infection, sinusitis, pollution, allergy, stress, etc. If the exciting factor can be identified, specific treatment (e.g. an antibiotic) can be given. Aerosol steroids (such as beclomethasone, Beclate) are not effective for acute asthma; drugs of this type help prevent worsening, but cannot stop all exacerbations from happening. An acute increase in symptoms may require a short course of an oral steroid (e.g. prednisolone) to bring it under control. Relief is provided by aerosol bronchodilators such as albuterol. Oral theophylline may help also. In very severe exacerbations an intravenous steroid must be given, along with large doses of inhaled albuterol; in such situations, oxygen should also be administered.