21 mo old, with a barking cough. Had a 103.0 fever thurs night none curret. Coughing so hard hes throwing up. Doc on thurs says he looks fne. Any idea?

URI. Sounds like he/she had a bad case of acute upper respiratory infection, which is now resolving. It may have been due to any of many bacterial or viral infections. If there's any concern at this time, please take him/her back to the doc.
More common . Things include croup, cold, bronchiolitis and less likely but more serious, epiglottitis. If fever persists, difficulty swallowing, excessive drooling - have him reevaluated.
Barking cough. My concern is that your child has croup - usually viral in nature - try putting them in a bathroom and runny the shower on hot - allowing the steam to build up. Allow them to remain for 5 minutes or so - and then - dress them and take them outside - sometimes the temperature change will break the coughing spasms. If not - if the fever returns - a trip to the ED might be necessary to treat.