The ablution becomes nullified by any of the following:
1.Natural discharges, i.e. urine, stools, gas, etc.
2.The flow of blood or pus and the like from any part of the body:
5.Losing one’s reason by taking drugs or any intoxicating stuff.
After the occurrence of any of these things the ablution must be renewed for prayer. Also, after natural discharges, water should be applied because the use of toilet tissues may not be sufficient for the purpose of purity and worship.