OCD sufferers often feel the need to wash their hands repeatedly.

obsessive–compulsive disorder

/ əbˌsɛs.ɪv kəmˈpʌl.sɪv dɪˌsɔ^rdə^r / noun

a psychological condition where a person has certain thoughts repeatedly or feels the need to perform certain actions repeatedly:
Obsessive–compulsive disorder affects about one person in forty at some point in their life.

The abbreviation is OCD:
OCD can be a very debilitating condition. | OCD sufferers often feel the need to check things repeatedly.