How many days is the danger period after neutering a male cat?

The first three days after neutering a male cat are the danger period; generally, if he is fine after 3 days he has passed it. During this period watch his spirits, appetite and the wound for redness or inflammation. If anything is off, go to the vet at once. Until the wound heals, check it daily, clear debris around it, spray anti-inflammatory medication, and keep the Elizabethan collar on to prevent scratching and infection.