They can be hard bumps or flat patches. Possible causes include milia, pityriasis alba, vitiligo, and more. Many people experience white spots on their face at some point during their lives.
The BBC's Analysis Editor Ros Atkins takes a look at how this has been playing out on the ground. Video produced by Catherine Karelli, Olga Robinson, Benedict Garman, Paul Brown and Yana Lyushnevska.
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