You should wash under there with lukewarm water or, if you absolutely feel the need to, gentle soap that is specifically made for cleaning your privates. Doing it with regular soap can cause issues.
Source: Have foreskin, washed with soap, talked with doctor.
Yeah, I call bullshit on this. Not washing under your foreskin is how you get an infection, not washing there too much.
You should wash under there with lukewarm water or, if you absolutely feel the need to, gentle soap that is specifically made for cleaning your privates. Doing it with regular soap can cause issues.
Source: Have foreskin, washed with soap, talked with doctor.
Soap bad, water only