Ways to ease cough

Seeing janelle cough non-stop, my heart ouch... Did some research online while she is sleeping to see if there are ways to ease her cough.

Here's what i found:

1. Your body needs vitamin C for its muscles, bones, cartilage and blood vessels; it also helps your body absorb iron. However, vitamin C does not necessarily improve cough symptoms. There are many potential causes of a cough, which include allergies, sinusitis or asthma, as well as a cold or the flu. Or a cough can be inherent of a more serious condition like emphysema, pneumonia, tuberculosis or even lung cancer. Vitamin C might improve a cough from some of these causes, but not from others.
   
   [Source] http://www.livestrong.com/article/493725-vitamin-c-to-stop-a-cough/#ixzz20ZO0HBbE
   
   There are posts where parents uses vitamin c to ease their child cough and it's works well.
   [Source] http://www.doctoryourself.com/coughing.html
   
   Recalled that Vitamin C is not able to store in the body, any excess C is spilled into the urine. But if too much of C might cause diarrhea too.
   
2. Essential Oil - Eucalyptus oil has long been respected for its ability to lower temperatures and help the respiratory tract by loosening and removing mucus during attacks of bronchitis, coughs, flu, sinusitis and throat infections. Its antiviral and antibacterial action will deter further growth of the bacteria or virus.
   
   Put a few drops of eucalyptus oil onto a hanky and lie it next to your pillow at night to help ease breathing.
   
   Caution ~ Eucalyptus oil may trigger seizure, hence anyone who has epilepsy should avoid the essential oils. [source] http://www.epilepsy.com/epilepsy/alternative_oils
3. There are old mothers tales that says put sugar into their porridge. My MIL always ask me to do that but i never did. Avoid sugar as bacteria will only multiply and feed on sugar.
4. Milk and dairy encourage the production of more mucous, so it's good to avoid. But for Janelle, cos she rejects water, so in order for her to intake enough water in a day, i diluted the milk for her.
   
5. Drink lots of water, at least 500ml of fluid as doctor recommended. Hot liquids can open up airways and moisturize a scratchy, dry throat in five minutes.
6. Put a good layer of  Vicks vapor rub on the soles of their feet and put socks on them. This product had been around for more than 100 years later, some still swear by the product.
   
   However, Vicks Vapor rub has it's Camphor Concerns. The reported side effects from swallowing health products containing camphor and/or eucalyptus oils vary from minor symptoms, such as burning sensation in the mouth, headache, nausea, and vomiting, to more severe and life threatening reactions such as seizures. Parents and caregivers who suspect that their child may have swallowed these substances should take the child immediately to the doctor or to the nearest health treatment centre. [Source] http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/life-vie/camphor-camphre-eng.php
   
   [Other source for reading] http://www.everydayhealth.com/cold-flu/vicks-vaporub-debate.aspx
   
   Eucalyptus oil can be found in Vicks vapor rub too

Anyone has better methods, please do share with me.. Many Thanks in advance.

Tried Vitamin C with Janelle, but it's her normal dosage and it seems to stop her cough for a short while.