Generally we ask that people wait 4 hours between swabs. This gives your cheeks time to recover and helps to give the lab a good backup sample just in case the first one does not yield results. However, we are usually able to get a good swab regardless of whether you have waited the 4 hours or not. If this happened, please go ahead and send us the samples! If we are unable to get a clear result from the samples provided, we will send you replacement scrapers.