How long does it take for the effect of pepper spray to wear off?

The timing of pepper spray's effects will vary from person to person, but it usually takes around 30 minutes for the symptoms to fade. The exact timing can range from 15 - 45 minutes, with eye irritation and redness lasting up to 24 hours. 

The first few minutes after an assailant is sprayed are when the effects are the strongest. You should use this time to get away from the threat and find help.