If your guinea pigs have short hair, then there is no need to cut their fur at all. It will follow particular growth cycles and each hair shaft will fall out of its own accord, and is unlikely to grow too long. If your guinea pig has long hair, then cutting it can make them much more comfortable and mean that you have to groom them less regularly. Long-haired guinea pigs whose hair is left long have tresses that tend to get very knotted and matted, with lots of bits of hay and food getting stuck that they are unable to remove themselves.
Some guinea pigs will needs hair cuts, whereas others will not
If you want to give your guinea pig a hair cut, be careful not to cut too close to the skin, and be extremely careful not to snip your guinea pig’s skin or ears. If you’re under the age of eleven or twelve we recommend getting an adult to do the hair trimming for you.