Cryotherapy is relatively low risk. There are a few side effects that may occur as a result of treatment including:
Pigmentary changes (hypo-pigmentation and hyper-pigmentation) if this happens skin colour normally returns after a few months.
Nerve damage (particularly in the areas where nerves lie close to the surface of the skin, on fingers, wrist, area behind the ear) Reports show that normal sensitivity returns after a few months.
Shards of frozen ice (minor shards of frozen ice may blow out, that will thaw on contact with healthy skin).
Hair follicle damage and permanent alopecia (especially when treating the area on sites with coarse terminal hair). Discuss are concerns you have with your clinician.