Thank you for your query on HealthCareMagic.
From what I gather there are two aspects to you query:
These two are different problems and need to be tackled accordingly. Fever, in any form, needs to be investigated and treated accordingly. The so called "feel nausea
after ride in the car" can be a part of the fever problem along with the cough
Before labelling the daughter as allergic to oat one should confirm it by giving a challenge test to oat.
I suggest you to discuss these aspects with the doctor.
I hope I have answered your query to your satisfaction.
Wishing all the best to your daughter.