Does Allergy Medication Cause Drowsiness?

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While some over-the-counter allergy medications don’t cause drowsiness, others can make it challenging to stay awake if you take them before bedtime. That is especially true if you’re taking other medications or have a preexisting medical condition that causes fatigue, like anemia, depression, or low blood pressure. Here are some of the most common antihistamines and decongestants and whether they have the potential to cause drowsiness in adults and children.

  1. First Generation Antihistamines

The first generation of antihistamines, like Benadryl, can cause drowsiness because they block histamine from binding to receptors in the brain. Histamine in the brain helps keep you awake, so blocking it will make you sleepy. However, different people react differently to these medications. Some are more sensitive than others and may experience side effects such as dizziness while using them.

It’s also crucial to note that the tolerance levels for these drugs are high, and with continued use, the user will build up a tolerance for the medication. That means if you’re taking allergy medication daily, your body is desensitized to the drug, leading to an increased risk of dependency. You can contact Prism Health Labs for reliable allergy tests to help you take control of your symptoms by determining what exactly you’re allergic to!

  1. Second Generation Antihistamines

The second generation of antihistamines, like Claritin, Zyrtec, and Allegra, are less likely to cause drowsiness because they primarily target the body’s histamine receptors instead of the brain’s histamine receptors. They work by targeting specific histamine receptors that are responsible for allergic reactions.

These newer antihistamine drugs are less likely to cause drowsiness and other side effects because they do not block histamine from binding with brain receptors but instead stop your body from producing it in excess amounts. Consequently, these medications may not affect one’s sleep patterns. However, though they cause less sedation than their predecessors, they are still classified as sedating antihistamines, which can cause drowsiness in some people.

  1. Nasal Spray Decongestants

Nasal decongestant sprays are a type of antihistamine that you spray up your nose. They can help relieve allergy symptoms like congestion and stuffy nose. They are not sedatives and will not cause drowsiness, but some people may experience sleepiness if they have taken them at bedtime.

The medication works on nasal passages without affecting your bloodstream, reducing the chances of causing drowsiness. If you’re taking any other drugs or have certain health conditions, talk to your doctor before using a nasal decongestant spray.

  1. Intranasal Corticosteroid

Using intranasal corticosteroids in treating allergic rhinitis reduces nasal congestion, sneezing, and itchy nose. Intranasal corticosteroids such as Flonase are safe and effective. They’re non-drowsy, but if you have trouble sleeping, be aware that this may also be a side effect of your medication.

However, intranasal corticosteroids may take a few days, so give them time before deciding if they’re working. Some people find that taking their daily dose late in the evening helps keep them alert during the day while their symptoms subside at night. Using this type of medication may be a good way of reducing the reliability of antihistamines.


Allergy medications are helpful, but they can have side effects. Understanding why antihistamines cause drowsiness will help you make better choices about which product you take and the best time to take your medication. Going for an allergy test from a reliable medical lab can help your doctor develop a working treatment plan for your allergies. It would help if you also changed your lifestyle to reduce environmental allergens and avoid triggers such as pollen, pet hair, and other allergens that may cause allergic reactions. When looking at antihistamine doses, it’s essential to realize that the higher the amount, the more likely you’ll experience side effects like drowsiness.

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