Single or infrequently repeated injections do not produce the long term side effects of continuous high dose oral steroid use which many patients fear. In my view, even multiple injections at one time are unlikely to cause significant or persisting problems. However, special care is needed with patients with diabetes, blood pressure or heart failure due to the effects of absorbed steroid and consideration given to the total dose given. Steroid leaking under the skin can cause thinning of the skin (subcutaneous fat atrophy). Occasionally, usually in young women, absorbed steroid can interfere with the menstrual cycle and this is occasionally quite troublesome for a cycle or two. IN the same group, steroid can cause a vascular flush or blush which looks like sunburn on the face or upper chest and may last a week or two.
Steroid spinal injections are usually aimed to be placed within the bony vertebral canal but outside the nerve membranes (the outermost of which is called the dura – hence the space within the bony canal but outside the spinal membranes is called the epi – [or around] dural space) where they are as a rule very safe. However, there is a long standing concern that misplaced injection within the spinal membranes could cause irritation of the delicate nerve roots at this level and result them becoming chronically inflamed (arachnoiditis) potentially leading to life-long pain. Such events are very rare and the true cause and effect relationship between injection and outcome is not clear but I would not dispute the possibility.