Driving After Taking Allergy Medicines

Driver taking benadryl pills while in the car.

Can you? Yes. Should you? Maybe not.

The answer requires a closer look at driving laws, as well as consideration of the type and amount of allergy medication taken and its impact on the driver. The Federal Drug Administration states that taking antihistamines may interfere with a driver’s ability to drive by slowing reaction time, making it hard to focus or think clearly, and causing mild confusion. Some antihistamines, such as Benadryl, can cause drowsiness and other conditions that may impair driving ability. Others may not.

In this article, I will address several popular antihistamines and whether or not people are likely to be impaired after taking them. And then I will discuss what to do after a car accident caused by a person who may be impaired because of antihistamine use. While I do not have a medical background, I have based my analysis upon the consumer information provided on the labels of the antihistamines, as well as information provided to consumers by the FDA.

Driving Under the Influence Laws Include Over-the-Counter Drugs

It’s illegal to drive while under the influence of drugs, alcohol, or a combination of the two in all 50 states. Many may assume that the word “drugs” refers to illegal drugs, but that is not necessarily the case. A person’s driving can be impaired by prescription medications and over-the-counter (OTC) drugs, such as antihistamines and cold remedies, as well.

The crime of driving impaired is commonly called “DUI” (driving under the influence), but many states use additional or alternative terms. South Carolina uses the DUI terminology, while North Carolina uses the acronym “DWI” (driving while impaired).

While the driving laws and penalties vary by state, some over-the-counter antihistamines can affect one’s driving ability by causing drowsiness, and driving while drowsy may be a crime.

Drowsy Driving Accidents Are a National Problem and Antihistamines May Be a Culprit

Trailing brake lights of a car crossing multiple lanes on a highway at night.A review of federal government websites reveals that drowsy driving has become a serious national concern. The National Sleep Foundation holds Drowsy Driving Prevention Week each year the week following the end of Daylight Saving Time. The National Safety Council (NSC) has a Driving Drowsy Prevention Week every November, and the National Highway Traffic and Safety Administration (NHTSA) has a website with many resources dedicated to battling the issue.

NHTSA reported that the number of fatalities involving drowsy drivers was 633 or 1.6 percent of total fatalities in 2020. The NSC compares driving while drowsy with driving under the influence of alcohol, stating that:

    • Drivers’ reaction times, awareness of hazards, and ability to sustain attention get worse as the driver gets drowsier


    • Drivers are 3x more likely to be in a car crash if they are fatigued


As discussed below, some antihistamines cause drowsiness, and there is a good chance that there are drivers on the roads who may be impaired after taking them. If you notice a driver weaving between lanes, drifting to the side of the road, hitting the rumble strip, or driving through stop signs, you may be witnessing a driver who is struggling to stay awake, potentially from using antihistamines. Stay safe by keeping your distance.

If you are hit by a driver exhibiting these types of behaviors who seems dazed and unfocused after the accident, you can inform the attending police officer and request that he or she look for signs of allergy or other medication in the car.

After the accident, call a car accident lawyer. An experienced attorney can guide you on next steps and advise you on whether you can seek compensation from the driver for your injuries. My firm will give you a free case evaluation if you call us at tel:1-866-900-7078 or contact us online.

Antihistamines Can Relieve Allergy Symptoms – And Impair Driving Ability

The main concern with antihistamines is that some can cause drowsiness, which can impair one’s driving. But each of the major brands of antihistamines may feature different key ingredients, and some are more likely to result in drowsiness than others.

Antihistamines are a class of drugs that help to treat allergy and hay fever symptoms, such as sneezing and a runny nose, and they can be categorized as first generation or second generation.

    • First generation antihistamines were approved by the FDA in the 1930s, and they work quickly to control allergy symptoms, but they easily cross the blood-brain barrier into the central nervous system and can cause sleepiness and other neurological symptoms, like having difficulty concentrating.


    • Second generation antihistamines were approved by the FDA in the 1980s, and this group does not cross the blood-brain barrier and has fewer side effects.


1st generation antihistamines include benadryl, dramamine & histex. 2nd gen ones include claritin, allegea, zyrtec & xyzal.

The main difference between first generation and second generation antihistamines is that generally the latter do not cause sleepiness in allergy sufferers and are considered safer because they interact better with other medications.

First Generation Antihistamine Benadryl Can Cause Drowsiness

Benadryl is an over-the-counter antihistamine that’s commonly used to help relieve allergy symptoms and itchy skin caused by hives and insect bites. The generic name for Benadryl is diphenhydramine, and it is an OTC first generation antihistamine.

Benadryl’s label states that when using this product:

    • marked drowsiness may occur


    • alcohol, sedatives, and tranquilizers may increase drowsiness


    • users should be careful when driving a motor vehicle or operating machinery*


*Check out the video NHTSA created to warn people of the dangers of drowsy driving associated with certain medications.

Because it can make people very sleepy, Benadryl can impair their ability to drive. Also, combining Benadryl with other drugs that also cause sleepiness can increase the risk for excessive sleepiness and makes driving even more dangerous.

Second Generation Antihistamines Claritin and Allegra Are Less Likely to Impair Drivers by Causing Drowsiness

Claritin (generic name loratadine) is a second generation antihistamine that can help to relieve symptoms of seasonal allergies without the side effect of drowsiness that Benadryl has. The product’s packaging labels it as “Non-Drowsy,” and the website claims that it is “the non-drowsy oral allergy brand that doctors recommend most.” Claritin’s label does indicate that “taking more than directed may cause drowsiness,” but there is no cautionary statement about driving a motor vehicle when taking it.

The antihistamine Allegra (generic name fexofenadine) also includes the “Non-Drowsy” label on its packaging, and it goes one step further than Claritin by not including any indication that drowsiness may occur as a side effect.

According to manufacturer information, it is less likely that drivers would be impaired if taking Claritin and Allegra as prescribed on the package versus Benadryl.

Second Generation Antihistamine Zyrtec May Also Cause Drowsiness in Drivers

Zyrtec (generic name cetirizine), however, is an exception to the rule when it comes to drowsiness and second generation antihistamines. When compared to Claritin and Allegra, studies have shown that people are more likely to be affected by drowsiness after taking Zyrtec than if they had taken Claritin or Allegra.

Zyrtec’s label messaging about drowsiness is similar to Benadryl’s and states:

    • drowsiness may occur (Note: Benadryl’s label said “marked drowsiness”)


    • alcohol, sedatives, and tranquilizers may increase drowsiness


    • be careful when driving a motor vehicle or operating machinery


While drowsiness may be less likely with Zyrtec than with Benadryl, it appears that Zyrtec can also impair a person’s ability to drive.

Highway sign that reads DON'T DRIVE TIRED.What You Should Do if You Think the At-Fault Driver Was Impaired by Antihistamines

So what does this mean to you? If you’re taking allergy medication, exercise caution. And if you have been hurt in a car accident caused by the other driver, and you suspect that the other driver may have been impaired from taking Benadryl, Zyrtec, or another antihistamine, be sure to mention this to the police officer at the scene of the accident. Negligence is negligence, and the other driver should be held accountable for any careless behavior that caused you harm.

If there is a criminal proceeding against the at-fault driver for driving under the influence, you can, and should, still proceed with your personal injury claim. And we can help you. If you are out of work because of your injuries and have mounting medical bills, we can grapple with these issues for you and fight for the compensation you may deserve. Call us at 1-866-900-7078 or contact us online for a free, no-obligation case evaluation.

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About the Author

Margo K. Carnahan is a personal injury attorney at the Law Offices of James Scott Farrin. She has 11+ years of experience as an insurance defense attorney and has worked on a wide variety of liability and workers’ compensation claims in North Carolina. Margo has an inside perspective on claim valuation from the insurance company side, and her empathy for accident victims drives her to be kind and compassionate with her clients. She is licensed to practice in the U.S. District Court for the Eastern, Middle, and Western Districts of North Carolina.