The Potential Dangers of Allergy Medication

As allergy season approaches, understanding allergy medications is crucial. Allergies happen when histamine overreacts to allergens, causing symptoms like sneezing and coughing. But it's essential to be aware of the dangers of allergy medication. First-generation antihistamines like Benadryl can impair cognitive functions and increase dementia risk. They also raise the risk of brain tumors with regular, long-term use. In contrast, second-generation antihistamines like Claritin have no such effects. Decongestants, often combined with antihistamines, can raise blood pressure and pose risks for those with heart conditions. Understanding the dangers can help you choose the right allergy medication with your doctor's guidance.

As allergy season ramps up, many people will reach for their allergy medications in the coming weeks. So what exactly are allergies? Your body has several defense mechanisms in place to ensure its safety. Your immune system is your body’s internal defense system that protects you from substances it determines to be foreign. Allergies occur when the chemical histamine overreacts to an allergen, like pollen and dust, causing symptoms like coughing, sneezing, and watery eyes. In 2018, 24 million people were diagnosed with seasonal allergic rhinitis (hay fever). There are several different types of medications that can prevent or negate allergy symptoms. Before choosing one, it is important to evaluate the dangers of allergy medication.

Allergy Medications and Their Dangers

To fully understand the dangers of allergy medications, you must understand the different types of allergy medication. Allergy medication comes in many different forms, including oral pills, nasal sprays, topical creams, and shots. Here are the most common forms of allergy medicine and the potential side effects you may experience.


Antihistamine is an over-the-counter or prescription drug that prevents the overreaction of histamine to allergens, thus preventing allergy symptoms like sneezing and coughing. Antihistamines are the most common form of allergy medication.

There are two types of antihistamines: first-generation (passed by the FDA in the 1930s) and second-generation (passed by the FDA in the 1980s). First-generation antihistamines, like diphenhydramine (Benadryl), work by blocking histamine receptors in the brain and spinal cord. They cross the blood-brain barrier, which causes drowsiness and loss of cognitive function. Second-generation antihistamines, like Lotradine (Claritin), do not cross the blood-brain barrier and do not cause drowsiness.

First-generation antihistamines present several dangers to your long-term health. The FDA warns against taking more than the recommended dosage of all allergy medications, but particularly diphenhydramine. This medication can cause serious heart problems and even death if taken at a high concentration. Diphenhydramine blocks the actions of acetylcholine, which is a neurotransmitter that is important for brain functions like learning and memory. Several studies show that it impairs cognitive functions such as alertness, attention, memory, executive function, reaction time, and vigilance. Additionally, studies show that regular use of diphenhydramine can increase your risk for dementia by 54%. There is also a 3.5 times increase in the risk of developing gliomas, a common type of brain tumor, with regular, long-term use of first-generation antihistamines.

Second-generation antihistamines do not cause long-term damage to the brain or any other organ system. In comparative studies, Desloratadine (Clarinex) was shown to have no effect on sleepiness, working memory, or reasoning. In a different study, Lotradine (Claritin) fared like a placebo in regards to cognition when compared to diphenhydramine.


Decongestant is a medication that constricts the small blood vessels in the skin and mucous membranes of the nose, ear, and mouth. It provides temporary relief of nasal and sinus congestion. Many oral allergy medications contain a decongestant and an antihistamine like Zyrtec-D (Cetirizine and pseudoephedrine) and Allegra-D (Fexofenadine and pseudoephedrine).

Decongestants pose serious dangers to people with high blood pressure, heart rhythm problems, and other heart conditions. The dangers of this allergy medication revolve around how it restricts blood vessels to provide relief from congestion. Most over-the-counter decongestants are not safe to be taken with most blood pressure medications. Because of the way decongestants restrict the blood vessels, these kinds of medication can raise blood pressure, increase pulse, and increase the risk for heart rhythm disturbance.

Other Forms of Allergy Medications

There are several other uncommon forms of allergy medication, such as corticosteroids and leukotriene inhibitors. Both work in different ways and have different purposes.

Leukotriene inhibitors inhibit a particular class of inflammation-producing chemicals called leukotrienes. This medication is typically used for asthma treatment but has been approved by the FDA for allergies. This type of medication is associated with a series of psychological side effects like hallucinations, depressive episodes, and suicidal ideation. If you experience any of these symptoms while on leukotriene inhibitors, contact your doctor immediately.

Corticosteroids relieve symptoms by suppressing allergy-related inflammation. Long-term use of topical corticosteroids can cause thinning skin and mucous membranes. Some powerful corticosteroids can cause disturbances in the hormonal levels of the body.

The dangers of allergy medication are real and serious. Luckily, your doctor can help you find the right medication to relieve your allergy symptoms. Talk to your healthcare provider today to see what type of allergy medication would work best for you!

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