Since radiation therapy is a localized treatment, the side effects will be localized to the treated area and are usually related to local inflammation of the skin that is incorporated into the radiation therapy field. Common reactions include redness, moist eczema in dogs, dry eczema in cats, itchiness and localized hair loss.
The skin irritation may start when your pet is halfway through the treatment protocol and should subside within an average of two to three weeks after radiation therapy is completed.
Regrowth of fur within the radiation treatment site may take months. In some cases, the fur may not fully regrow or, if the fur does, it may be a different color (usually white or gray).
Occasionally organs that are within or adjacent to the radiated site may have some complications. This can be anticipated and discussed before the radiation treatments begin.