First and the foremost, you need to understand what CPT means. The abbreviation CPT stands for Complete Protection Time. You will usually find CPT as part of the labels on mosquito repellents. Most people blindfoldedly opt for repellents that have long protection hours, but this is not recommended. Do not go for anything that has more than 6 hours of CPT. Remember, you do not want the chemicals to be on your skin for long. These chemicals can be harmful so you need to get them off as soon as possible.
Look out for active ingredients in the repellent you are going for. Most mosquito repellents usually consist of synthetic chemicals or plant based chemicals. You will find DEET as the most common chemical in mosquito repellents. DEET is a controversial element of repellents but there is not enough proof to declare DEET dangerous. Therefore, do not be intimidated by it.
Try to go for organic repellents which are now easily available in the market. These might not be as effective as chemically enhanced repellents but they are less harmful to your skin.
Make sure you know how effective the repellent would be. Some repellents are not highly concentrated and they are meant for light usage. Others can be highly concentrated and are not meant to be used for standard conditions. Do not go for the ones that promise big. Instead, buy a repellent that suits your needs most.