Measles

According to the CDC, 'Measles is an acute, highly communicable viral disease with prodromal fever, conjunctivitis, coryza, cough, and Koplik spots on the buccal mucosa. A characteristic red blotchy rash appears around the third day of illness, beginning on the face and becoming generalized. Measles is frequently complicated by middle ear infection or diarrhea. The disease can be severe, with bronchopneumonia or brain inflammation leading to death in approximately 2 of every 1,000 cases.'

Fortunately, measles can be prevented by the MMR (Measles | Mumps | Rubella) vaccine. Keep in mind that 'measles remains a common disease in many countries of the world, including some developed countries in Europe and Asia.'

Keep in mind that many viral infections cause a 'red blotchy rash,' measles is rare in the United States, especially as most kids are immunized, so unless your child has the whole pattern of measles symptoms described above, then you likely don't have to worry about measles every time your child gets a rash.