Is he who urinates involuntarily upon water touching his body (due to an allergy to water, not persistent urinary incontinence) considered to have lost the ability to use water, and is he permitted to abandon prayer?

The ruling for this person is to perform ablution (wudu') with water, and what comes out of urine does not harm him, because he is in the ruling of سلس ( سلس البول, urinary incontinence). Some jurists have also held that his ruling is tayammum (dry ablution), and as a matter of precaution, he should combine both. As for abandoning prayer, it is a great danger, and he must hasten to repent to Allah Almighty. He must also make up all the prayers he missed according to the majority of scholars. If he knows their number, he should make them up; otherwise, he should continue to make them up until he is reasonably certain that his obligation has been fulfilled.