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red bump for 30 minutes indicate allergic one
in some case itching may be absent .
its better to identify by what it happen?like food ,drug,inhalant or any other .
take tab allegra
180 once a day ,it will be better
ask her to avoid sun exposure,out side food
drink lot water and better to consult dermatologist
if it persisit
but nothing to worry
i hope i answered your question