More than 6 million children under the age of 18 have asthma. The majority of kids with asthma develop symptoms by age 6, and many even develop symptoms by age 3. If your infant has a cold and is wheezing, you may be wondering if the problem is asthma. But it's not always clear if an infant has asthma. More important than getting a firm diagnosis is making sure your child gets treated for any breathing problems that occur.