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I'm not aware of classical solution, but have you try Gaussian filter and compute the difference? Hotspots should lied on high differences?

I see on pictures than not only hotspots are remove, the whole skin is kind of ``photoshoped''. Maybe a good solution will be to convert your image in HSV and filter on luminance channel. Use a segmentation of that color (the whole color, to have the skin for example) and applied the processing on the whole component. Segmentation that used seed would be a good starting point, you pick seed in each high luminance part. Moreover, if your are only finding hotspots on skin, try a skin detector in a first step.