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I wonder whether it has any relation to Dengue
at all. Just because a thing happened after another, it does not mean that the first one is the cause of second > it could be a mistaken assumption - "post hoc ergo propter hoc" (after this therefore because of this).
It will be wiser to see a dermatologist
If necessary have more tests.
There are several reasons for a rash
/ there are several kinds of rashes!
Wishing you speedy recovery