Vicks VapoRub doesn't relieve nasal congestion. But the strong menthol odor of VapoRub tricks your brain, so you feel like you're breathing through an unclogged nose. By contrast, decongestant tablets and nasal sprays sold over-the-counter appear to narrow blood vessels in the lining of your nose, leading to reduced swelling in your nasal passages.

VapoRub has drawbacks other than its ineffectiveness as a nasal decongestant. It's unsafe for any use in children under 2 years of age. In children under the age of 6, use it only on the neck and chest.

Swallowing a few teaspoons of camphor — one of the main ingredients in VapoRub and other topical medications, such as Campho-Phenique and Bengay — can cause fatal poisoning in toddlers. Topical camphor absorbed through mucous membranes or broken skin also can be toxic. That's why you should never put VapoRub in or around the nostrils — particularly a small child's nostrils. Finally, if VapoRub gets in your eye, it can injure your cornea.