If you go onto many online pet stores and some brick shops, you will likely see guinea pig accessories such as collars and harnesses to let you walk them. The idea of selling something unsafe doesn’t sit right, so we would assume they are. However, there is a debate about the safety of guinea pig harnesses and safe to use. Guinea pigs have very delicate neck bones; thus, it can be extremely dangerous for them to wear things around their necks.
With that in mind, unlike dogs, you should NEVER put a collar on a guinea pig; even if you do see them in shops, you will be causing more harm than good. Harnesses, on the other hand, do not go around the guinea pig’s neck. So, if you get the right one, you can use them quite safely. Be sure to buy an H harness and one made of mesh if you can. Furthermore, you need to ensure that it fits them well. If you can still get a finger between the harness and their body, it should be fine. But, make sure to look out for signs of damage, such as increased irritability, loss of hair, and fear.