What Exactly Does DayQuil Do? – A Go-To Resource for Cold and Flu Relief

As a practicing pharmacist, I often field questions about over-the-counter medications. One of the most frequent topics is DayQuil, a common remedy for cold and flu symptoms. People are curious to understand what exactly it is, how it works, and its potential side effects.

In this article, we will journey through the intricacies of DayQuil, explore its active ingredients, and examine how they synergize to combat the unpleasant symptoms of colds and the flu. We will also compare it to its companion product, NyQuil, and delve into their differences.

Overview of Cold and Flu

Cold and Flu

Colds and the flu are two of the most common illnesses that we experience. As we explore DayQuil, it’s crucial to understand what these conditions are and how they affect our bodies.

Colds and flu are both viral infections that affect the respiratory system. They have similar symptoms, including congestion, runny nose, and sore throat. However, flu symptoms are generally more severe and may also include fever, body aches, and fatigue. The flu can sometimes lead to more serious complications, like pneumonia, particularly in people with weakened immune systems.

While over-the-counter medications like DayQuil are commonly used to manage symptoms of colds and flu, it’s essential to be aware of other conditions, such as Lyme disease and its co-infections, which can present with overlapping symptoms and require a different approach to treatment.

While there’s no cure for the common cold or flu, medications like DayQuil can help manage symptoms and make you feel better while your body fights off the virus.

The Basics

cold and Flu

DayQuil is an over-the-counter medication designed to help alleviate many of the common symptoms associated with cold and flu. It’s produced by Vicks, a renowned healthcare brand owned by Procter & Gamble. It is popular because it effectively eases symptoms without causing drowsiness, allowing users to go about their daily routines.

DayQuil is a multi-symptom relief medicine, which means it’s composed of multiple active ingredients. Each of these ingredients is targeted toward relieving a specific symptom of the common cold or flu. The combination of these ingredients makes it an effective option for many individuals suffering from these ailments.


Each ingredient in DayQuil is designed to target a specific symptom. We’ll examine three primary active ingredients: Acetaminophen, Dextromethorphan, and Phenylephrine.


Acetaminophen health

Acetaminophen is a pain reliever and a fever reducer. It works by changing the way your body perceives pain and by cooling your body.

This common drug is used in many over-the-counter and prescription medicines. In DayQuil, it helps to reduce any discomfort you might feel from a sore throat, headache, or body aches, and it can also help to lower a fever if you have one.


Dextromethorphan is a cough suppressant. It operates by affecting the signals in the brain that trigger the cough reflex.

By suppressing this reflex, dextromethorphan helps to reduce the urge to cough. This can be particularly beneficial if you have a persistent dry cough that’s causing discomfort or preventing you from getting on with your day.


runny nose

Phenylephrine is a nasal decongestant. It works by shrinking swollen blood vessels in the nasal passages, allowing you to breathe more easily.

When you have a cold or the flu, your nasal passages can become inflamed, causing that stuffy nose feeling. Phenylephrine is designed to alleviate this symptom, making it easier for you to breathe.

How It Works

Understanding the mechanisms behind DayQuil allows for a greater appreciation of its benefits.

DayQuil, through its combination of ingredients, targets a variety of symptoms simultaneously. Each ingredient functions differently, but together, they provide a comprehensive solution for cold and flu relief. Acetaminophen works to relieve pain and reduce fever, Dextromethorphan suppresses the urge to cough, and Phenylephrine relieves nasal congestion.

The fast-acting nature of these drugs means relief often starts within 20-30 minutes after taking DayQuil. As a non-drowsy formula, it does not contain antihistamines, which are commonly associated with sleepiness. Therefore, it allows those taking the medication to continue their day without experiencing sedation.

DayQuil VS NyQuil

cold and flu symptoms

To further comprehend the effectiveness of DayQuil, let’s compare it to its nighttime counterpart, NyQuil.

DayQuil and NyQuil have similar ingredients and serve the same purpose – alleviating cold and flu symptoms. However, there’s one significant difference: the inclusion of an antihistamine, doxylamine succinate, in NyQuil. This ingredient is effective at relieving runny nose and sneezing, but it also tends to cause drowsiness. This makes NyQuil suitable for taking before sleep.

As previously stated, DayQuil is non-drowsy and is designed for daytime use to keep you functioning throughout your day. It’s essential to use these medications as directed and intended, taking DayQuil during the day and NyQuil before sleep.

Potential Side Effects

Like any medication, DayQuil can potentially cause side effects. Being aware of these can help you make informed decisions about your health.

Common side effects include mild headache, dizziness, feeling nervous or anxious, and upset stomach. Serious side effects are rare but can include allergic reactions, severe dizziness, rash, itching/swelling, severe stomach/abdominal pain, and easy bruising/bleeding.

While serious side effects are uncommon, it’s essential to contact a healthcare professional immediately if they occur. Also, prolonged use of DayQuil, especially in high doses, may lead to liver damage due to the acetaminophen content.

How to Use It Safely

healthcare professional

Although DayQuil is an over-the-counter medication, it’s essential to use it safely and responsibly to avoid potential risks.

Always follow the recommended dosage on the product’s label, and do not exceed this dosage unless directed by a healthcare professional. In general, this means taking no more than four doses in a 24-hour period.

Additionally, it’s crucial to consider other medications you may be taking. DayQuil can interact with other drugs, potentially leading to dangerous side effects. This is particularly true for medications that contain the same active ingredients as DayQuil. Always check with a healthcare professional if you’re unsure about drug interactions.


What is DayQuil used for?

It is used to treat nose stuffiness, relieve coughing, and ease pain and fever.

What are the active ingredients in DayQuil?

The active ingredients are Acetaminophen, Dextromethorphan, and Pseudoephedrine.

What should I tell my doctor before taking DayQuil?


You should inform your doctor if you are allergic to any of the ingredients in DayQuil if you have taken certain drugs for depression or Parkinson’s disease in the last 14 days, if you have a cough with a lot of mucus, if you have a long-term cough caused by smoking or being around smoke, or if you have liver disease.

What should I avoid while taking DayQuil?

You should avoid taking other products that contain acetaminophen as it may cause liver problems. Also, avoid alcohol while taking it.

How should I take DayQuil?

It can be taken with or without food. If it causes an upset stomach, take it with food. Always follow the dosage instructions provided by your doctor or pharmacist.

What should I do if I miss a dose of DayQuil?

If you miss a dose and it’s close to the time for your next dose, skip the missed dose and go back to your normal time. Do not take 2 doses at the same time or extra doses.

Can I take DayQuil if I am pregnant or breastfeeding?

pregnant mamy

If you are pregnant or breastfeeding, you should discuss the benefits and risks of using it with your doctor.

How should I store DayQuil?

It should be stored at room temperature, protected from heat, and kept in a dry place. It should not be stored in a bathroom.

What should I do in case of an overdose?

If you suspect an overdose, call your local poison control center or seek medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

Closing Thoughts

DayQuil offers a comprehensive solution for managing the symptoms of the common cold and flu. Its combination of ingredients works synergistically to provide relief from pain, fever, cough, and congestion, helping you continue your day with minimal disruption.

However, as with all medications, it’s crucial to use DayQuil responsibly. Always adhere to the recommended dosage, and consult with a healthcare professional if you’re taking other medications or if you experience any severe side effects.