There are certain types of warts that should never be self-treated:
Plantar warts in large clusters, or single warts more than half an inch
Venereal (genital) warts.
Flat warts (they are too easily confused with other skin conditions, and
usually go away completely by themselves after a few months).
If self-treatment of common warts is ineffective after four weeks, or
plantar wart treatment ineffective after 12 weeks, a physician should be consulted. Corns
need only to be evaluated by a physician if they are particularly persistent and very
painful. Custom orthotic inserts may be considered.