Oral steroids enter the bloodstream to get to the lungs, so they can cause these and other systemic effects, particularly if used frequently or for long periods of time. Other effects include cataracts, increased blood sugar, lack of blood supply to some bones and suppression of the body's own production of steroids needed during stress. Since inhaled steroids reduce the amount of oral steroids that may be needed for asthma, they may be safer than just using as needed mediation in all but the mildest forms of asthma. If your child is given many courses of oral steroids, careful monitoring for some of these side effects may be necessary.
Glucocorticoids are potent anti-inflammatories, regardless of the inflammation's cause; their primary anti-inflammatory mechanism is lipocortin-1 (annexin-1) synthesis. Lipocortin-1 both suppresses phospholipase A2 , thereby blocking eicosanoid production, and inhibits various leukocyte inflammatory events ( epithelial adhesion , emigration , chemotaxis , phagocytosis , respiratory burst , etc.). In other words, glucocorticoids not only suppress immune response, but also inhibit the two main products of inflammation, prostaglandins and leukotrienes . They inhibit prostaglandin synthesis at the level of phospholipase A2 as well as at the level of cyclooxygenase /PGE isomerase (COX-1 and COX-2),  the latter effect being much like that of NSAIDs , potentiating the anti-inflammatory effect.