Side effects of Vicks Formula 44D include vomiting, nausea, dizziness and headache, according to WebMD. Patients should stop taking the medication and inform their doctors if they experience insomnia, nervousness or confusion. Other rare but serious side effects include rapid, pounding or irregular heartbeat, seizures, hallucinations, tremors and problems urinating.
Head pain, loss of skin color and excessive sweating are rare side effects, but they can be severe. A severe allergic reaction to Vicks Formula 44D is also possible but unlikely, notes WebMD. If symptoms such as facial itching, swelling of the tongue and throat or breathing problems develop, patients should seek emergency medical attention.