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Though you say that it is not sun exposure the red patches locations indicate it is a sun exposed area. Hence I partially attribute this to sun exposure also. The other possible causes could be allergic reactions to unknown substances, skin hypersensitivity
, eczema, dermatitis
The cause can also be ruled out if it is sudden onset or gradual.
lotion over them and if not seek a dermatologist
opinion for steroid prescription.
Hope it helps.