Yes, vicks can further irritate the mucous membranes of young children. A regular old steam vaporizer (out of reach) or a humidifier may provide him some relief.
IF your ENT does prescribe something like Singulair or Zyrtec, beware that there are some off label side effects in some children--we tried a couple of things with my daughter around a year, but she had serious personality changes and night terrors. She did get tubes in her ears around a year due to constant ear infections.
Is your son in daycare? Based on my daughter's rapid and continued improvement of "allergy" symptoms since I changed her daycare, I think there was something there that was affecting her. Her perpetually runny nose and goopy eyes cleared within 4 days of her starting in a new facility.
I am not hyper-sensitive about chemical use, though we don't use much in the house. But, if you haven't already, consider that your laundry detergent/fabric softener or some other cleaning agent may be disrupting his system.