What form of ionizing radiation in high doses causes delayed irreversible changes of the skin?

All ionizing radiation in high doses causes irreversible changes to the skin...In some cases the change is caused by death.

Say, for instance, that you were exposed to Alpha radiation, it would not penetrate deeply enough to pass through the dead skin cells. If you ingest an Alpha emitter, it could have lethal effects.

Beta is perhaps the most dangerous. It penetrates deeply and causes damage to the DNA that can be expected to lead to skin and other cancers. On the other hand, Beta radiation is used to destroy tumors.

Gamma radiation, same as X-rays, causes damage that, like Beta, is not limited to the skin.

It has been said that there is no safe dose of radiation.