how long to keep the dressing on before changing it.? Can it be removed for wound clean and put it back on?

Hydrocolloid dressings are designed to be left on for several days, typically between 3-7 (this is only in general; individual manufacturers may recommend a slightly different timeframe). However, this is only advisable if the dressing remains fully intact, less than 70% saturated and the wound is NOT infected. If the dressing is becomes detached for ANY reason (Eg: Falls completely off, starts to peel at the corner, or is intentionally removed), it’s considered “compromised” and must be disposed of. NEVER PUT IT BACK ON.

How thick are these patches?

Measured "X-Thin" size with a micrometer: ~0.5 mm thick dressing (0.67 mm dressing + liner; 0.17 mm thick liner)

Is the patch waterproof? Does it stays even after showering

Yes it stayed on without any problems at all.

Search for Med Pride and call the 800 # on their site. There is no mention of latex on that page or the package that I can see. It feels like vinyl, but, I forgot one and it became a permanent part of my sock, so it could be latex. I just know they work and I want a larger size for my leg ulcers.