Learn more about the 9 most common food allergies. A rash resembling large purple patches or dark bruises can indicate a serious condition, such as vasculitis and deep vein thrombosis. A medical ...

Medically reviewed by Archana Sharma, DO Although rare, a red rash may indicate leukemia, which is a type of blood cancer. A leukemia rash can look like tiny dots, big plaques, or itchy bumps that do ...