This combination medication is used to temporarily treat symptoms caused by the common cold, flu, allergies, or other breathing illnesses (such as sinusitis, bronchitis). Dextromethorphan is a cough suppressant that affects a certain part of the brain, reducing the urge to cough.

The bottom line. Nyquil contains the active ingredients acetaminophen, dextromethorphan HBr, doxylamine succinate, and sometimes, phenylephrine HCl. Doxylamine is the main ingredient that causes sleepiness. There's no evidence to support using Nyquil as a sleep aid.

Vicks NyQuil SEVERE Cold, Flu, and Congestion Medicine, 2x12 fl oz Twin Pack, Berry Flavor, Maximum Strength, Nighttime Relief.

Doxylamine Succinate This medication is an antihistamine found in a variety of over-the-counter cold and flu medications. Doxylamine works by blocking the activity of histamine throughout the body. Histamine is produced by the immune system to help combat infections, and it also helps the body stay awake.

Taking NyQuil can make people drowsy and fall asleep, which is the major side effect of the drug. The duration and quality of sleep can vary depending on the person. Other, rarer, side effects are mainly due to the acetaminophen component and can include: Skin reddening.

NyQuil can cause you to feel very drowsy or sleepy and you may fall asleep after taking it. Be careful when driving or operating machinery if you have taken this product. Avoid drinking alcoholic beverages with NyQuil. Alcohol, sedatives and tranquilizers can increase drowsiness when used with NyQuil.

Taking NyQuil can make people drowsy and fall asleep, which is the major side effect of the drug. The duration and quality of sleep can vary depending on the person. Other, rarer, side effects are mainly due to the acetaminophen component and can include: Skin reddening.

How long does Nyquil's drowsiness last? Nyquil's active ingredient, doxylamine, which has antihistamine and sedating effects, can lead to sleepiness. Nyquil can cause different degrees of sleepiness, depending on the individual lasting anywhere from 4 to 6 hours on average.

NyQuil can cause you to feel very drowsy or sleepy and you may fall asleep after taking it. Be careful when driving or operating machinery if you have taken this product. Avoid drinking alcoholic beverages with NyQuil. Alcohol, sedatives and tranquilizers can increase drowsiness when used with NyQuil.

For most people. Although lingering drowsiness is a common side effect, many people who take NyQuil experience nervous anxiety instead. This occurs most often with younger people, which is why parents are warned not to give NyQuil to children under age 12.

How long does Nyquil's drowsiness last? Nyquil's active ingredient, doxylamine, which has antihistamine and sedating effects, can lead to sleepiness. Nyquil can cause different degrees of sleepiness, depending on the individual lasting anywhere from 4 to 6 hours on average.

The bottom line. Nyquil contains the active ingredients acetaminophen, dextromethorphan HBr, doxylamine succinate, and sometimes, phenylephrine HCl. Doxylamine is the main ingredient that causes sleepiness. There's no evidence to support using Nyquil as a sleep aid.