Is the very small amount of fluid that exits the penis when thinking about or seeing something arousing, a nullifier of ablution (wudu'), and is it necessary to change one's underwear if it touches them?

What is discharged from the ذكر (male organ) upon looking at a woman or fondling her is madhiy, which is impure (najis) and invalidates ablution (wudu') by scholarly consensus. The body and clothing must be washed from it, and no exemption is granted for a small amount of it, according to the preponderant opinion.