X-radiation is a form of ionizing radiation (since it carries enough energy to liberate electrons from atoms, thus ionizing them) that penetrates the living tissues and can cause changes in the molecular structure of the living cells, making them dysfunctional or functionally inactive (somatic effects) and can result in mutations (genetic effects) or even destruction of the cells (apoptosis). These effects depend on the type of radiation received, its size, the rate at which radiation is received, the part of the body that is exposed and the age of the individual exposed to it. The biological effects of X-rays can be classified by the following categories:
Reversible changes: the earliest and most common, including reddening of the skin (erythema), skin pigmentation (which can eventually be an irreversible change) and loss of hair (epilation).
Irreversible changes: caused by high radiation of the proper energy which can result in permanent destruction of a tissue (specially the skin) or molecular/structural changes. It includes radiation dermatitis, radiation cancer (risk of solid cancers and leukemia), anemia (due to irradiation of bone marrow), poor digestion and absorption of nutrients (when the GI tract is affected), and cataracts of the lenses of the eyes. Sometimes it can also affect reproductive organs and cause increased rates of stillbirths, miscarriages, infant death and birth defects.
This is the reason why X-ray professionals need to follow radiation protection actions (including shielding, using protection devices, and the use of a radiation dosimeter to monitor received radiation).