Short answer
No. Touching something impure, such as urine, a dirty diaper, pork or a dog's saliva, does not break wudu in any of the four schools. You only need to wash the impurity off before you pray. Ghusl is not needed either.
Touching najasah does not break wudu or require ghusl. The touched place becomes impure if wet impurity or its trace is on it, and it must be washed before salah if it is beyond the excused amount.
The four schools agree on this.
Explanation
Wudu (ablution) is about your state, and najasah is dirt on you; the two are separate (see hadath and najasah). When a Bedouin urinated in the masjid, the Prophet ﷺ had a bucket of water poured over the spot. The impurity was dealt with by washing, and nobody was told to renew wudu for being near it.
Common cases:
- Changing a diaper or cleaning up after a child: wash your hands; wudu stays.
- Handling raw pork or other haram meat at work: wash your hands; wudu stays. Wear gloves if you can.
- A dog's wet nose or saliva: wash the spot; wudu stays (see touching a dog).
- Stepping in urine barefoot: wash your foot; wudu stays.
- Touching dry impurity with a dry hand: nothing transfers, so there is nothing to wash.
Touching only affects wudu through a different rule: in the Shafi'i and Hanbali schools, touching your own private parts with your hand breaks wudu, but that is about the private parts, not about impurity. For a Hanafi, washing your private parts after wudu does not break it either.
If impurity got on you and you prayed without noticing, see praying with impurity on clothes. The four schools agree that touching impurity does not break wudu.
The evidence
Sahih al-Bukhari 220
Sahih... دعوه وهريقوا على بوله سجلا من ماء ...
"Leave him, and pour a bucket of water over his urine."
Impurity is removed by washing the place.
Where the ruling is recorded
- Nur al-Idah with Maraqi al-Falah, Kitab al-Taharah, section on what does not break wudu. Lists things that do not break wudu.
- al-Hidaya, Kitab al-Taharat, chapter on impurities and their purification. Impurity is removed by washing.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.