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Thank you for this question.
This sounds most closely like your hamster has mites. The mites cause red bumps that are very tiny and mke ilook like a red rash or redish skin. They create hair loss. This is a common affliction.
the mites would be gone if you use an anti mite spray. Disinfect the whole cage and apply some anti-mite spray on the hamster bedding and on the hamster. Do not apply the spray directly on the hamster but apply some on a small brush, comb the brush on the hamster and then use a small cloth or tissue paper to dry off the hamster.
This information has come from: http://www.hamster-club.com