Is it all right to use Vicks Vaporub on a 4-year-old child who has asthma?
Vicks Vaporub is a topical medicine designed to relieve cough in cases of the flu and colds. It is considered safe for kids age 2 years and older, provided you follow the package directions carefully. However, Vicks will not relieve an asthma cough in a child with asthma.
It is important NOT to rely on over the counter formulas such as Vicks to treat asthma. It could be used as a supplemental treatment, I suppose, though I would encourage you to discuss that with your child's doctor. But for effective asthma treatment, your child will need to be taking an inhaled steroid of some type. That is the only way to achieve reliable and consistent asthma control, especially during times of illness, and will keep your child healthy.
Here are some articles that you might find helpful:
How to Asthma-Proof Your Home
10 Tips for People Newly Diagnosed with Asthma
10 Essential Asthma Terms You Should Know