cough

Cheryl works as an nurse at a nursing home. She is constantly around sick old people.
For about a year she has had a persistant cough that starts at 4pm, especailly on the days that she works. On the third day off she has just about gotten the cough to stop.
We started her on Raven. She loved the wonderful warm feeling on her chest and it stopped the cough within two minutes. Raven has eucalyptus radiata and raven sara in it. Well she called me and was out of her Raven and coughing her head off. I had RC on hand. I thought it would work just as good for her. It has Eucalyptus globulus, E radiata, spruce, citriodora and pine in it.
RC stands for respiratory control so we gave it a try. It made the cough worse and didn't help at all. What do you all think? Got any ideas why if did not work?