Periods of worsening may occur due to infection. In these cases, antibiotics are recommended. Common antibiotics used include amoxicillin, erythromycin, or doxycycline. Antibiotics, such as erythromycin, may also be used to prevent worsening of disease. Airway clearance techniques, a type of physical therapy, are also recommended. Medications to dilate the airways and inhaled steroids may be used during sudden worsening, but there are no studies to determine effectiveness. There are also no studies on the use of inhaled steroids in children. Surgery, while commonly done, has not been well studied. Lung transplantation may be an option in those with very severe disease.