Steroids have extreme and far-reaching effects on many systems of the body.

Immune system
* Reduce functions and numbers of T and B cells and other lymphocytes and macrophages
* Cause atrophy of the lymph nodes and the thymus gland, and increase the incidence of infections by opportunistic pathogens
* Increase the incidence of cancer
* Alter lymphocytes
* Suppress the body’s reaction to antigens (foreign invaders) and decrease access of lymph cells to antigens at sites of inflammation
* Increase the incidence of lymphoma
* Reduce the release of monocytes and macrophages from bone marrow and their numbers in circulation
* Decrease the body’s ability to clear itself of bacteria or fungi
* Cause death of leucocytes.

Adrenal glands
* Cause adrenal insufficiency.

Respiratory system
* Inhaled steroid aerosols (such as Beclovet) increase infections with Candida albicans and/or Aspergillus niger in the mouth and pharynx and, occasionally, in the larynx. A positive culture for oral Candida may be present in up to 75 per cent of patients.

Skin
* Cause delay in wound-healing
* Cause a variety of skin changes, including acneform eruptions, atrophy, stretch marks
* Increase the risk of bacterial, yeast and fungal skin infections
* Increase the incidence of Kaposi's sarcoma.

Muscle and bone
* Cause muscle weakness and bone disorders
* Interfere with growth of bone, muscle and other tissues.