The idea is basically a shape shifting entity that manifests as a certain type of medical supply, such as a bandage, splint, or syringe. This is dependent on who uses the SCP i.e. for a person with a stab wound it would manifest as a bandage, for a person with a cold it would manifest as cold medication. The SCP possesses healing properties, and will completely any injury or ailment. However, about 1 month after treatment, the injury would return, and the SCP would have to be used to treat it again. The amount of time after treatment when symptoms reappear would decrease, creating a dependence on the SCP, almost like an addiction. Eventually, the SCP would fail to heal the ailment, and the ailment would progress and get worse until death. The Foundation is not immediately aware of this property, and so use of the SCP as a medical aid in facilities leads to plenty of casualties. This is just a rough idea, let me know what you guys think!
I'm not sure that's been done before, but I'm not sure the skip would be used in that way by the Foundation. The moment they realized it was only temporary they'd stop and use more permanent solutions. However, if you like working with biomedical ideas, please do so. I like biomedical technologies, and I'm pretty sure there are more on the wiki who do. But do keep in mind, people get very tired of objects that simply kill you as their anomalous property, or in addition to their anomalous property, and this does have a touch of 'thing that kills you.'
To add to what LadyKatie has said, consider building it as part of a narrative or theme. If you want the cure to be one that loses effectiveness over time, pushing the user toward addiction, then spend some time contemplating what addiction to a cure is like.
Of course, we have lots of examples of that in the medical profession. Perhaps not in bandages, but in prescription medications. But that won't stop us from using bandages in this story. So, why is someone getting addicted? Well, it's because the bandage's effectiveness wears off. So, the cure must be ongoing. The wound remains. If you think of this like any drug that is prescribed for eternity, this makes sense.
But what's really going on, then? There would need to be some condition that the treatment does not actually cure. It's a palliative, a support, but not the solution. On the other side, what is this wound in the first place? Is it something that needs to be fixed, but cannot? When there's a problem of something that needs to be fixed, but cannot, what's really going on? Are we lying to ourselves? Hoping to survive long enough for the situation to change and it becomes possible to resolve?
I'm just scratching the surface here, but this is the sort of brainstorming that allows for the narrative you want to tell, and the themes you want to explore, to become evident.