Allergens and Antihistamines

Allergens and Antihistamines

October 12, 2022

Woman blowing her nose on a sofa.

According to the Centers for Disease Control and Prevention, 27 million Americans have some form of hay fever. Another 52 million suffer from sinusitis or bronchitis. That means one in five people have allergies, not including those diagnosed with asthma.

Sensitivity or exposure to an allergen can create an allergic reaction. An allergen is any substance, such as pollen, that induces an allergic reaction. And hay fever is just one type of allergic reaction. Many other pollens, molds, spores and plant-based materials can cause seasonal allergies. Other types of allergens, such as bee stings, insect bites, dust and food, can result in a severe and sometimes deadly allergic reaction known as anaphylaxis.

This article focuses on seasonal allergens, the allergic reactions they cause and their treatment.

Symptoms of seasonal allergies

Seasonal allergies can cause problems for people of any age. Exposure to allergens can cause:

  • Sinus headaches
  • Itchy, watery eyes that make it difficult to focus or see
  • Breathing problems
  • Sinus and ear infections
  • Sore throat, which can lead to strep throat
  • Sneezing, chest congestion and coughing
  • Skin rashes and itching
  • Chest pain

These symptoms can disrupt a person’s sleep and ability to focus.

What happens when someone is having an allergic reaction?

When a person is exposed to an allergen, a chemical reaction occurs in the body. The allergen is most often a protein that the body doesn’t recognize, setting the body in attack mode. This causes the body to release histamine, a naturally occurring chemical that goes into overdrive when an allergen protein is discovered. An overproduction of histamine can cause unwanted side effects, such as:

  • Expanding blood vessels, causing dizziness or fainting
  • Increased heart rate, making the heart pump too fast
  • Muscle contractions, causing coughing and constriction of the throat and other organs
  • Swelling, which can reduce air exchange


Taking an antihistamine slows or reduces the histamine side effects, lessening the symptoms of the allergic reaction. Antihistamines attach to histamine receptors in the body, which directly impacts the central nervous system. It is because of this attachment that antihistamines can also cause:

  • Drowsiness
  • Dizziness
  • Slowed cognitive and motor responses (A person actually thinks and moves slower while under the influence of an antihistamine.)

Before you take an antihistamine, know that it can impact your ability to drive or operate equipment. Often, people feel tired and need to take a nap to restore energy levels. Examples of common first-generation antihistamines include Benadryl, Dimetane, Unisom and Triafed.

Second- and third-generation antihistamines generally do not have sedative properties. These medications provide relief without impacting the central nervous system. Examples include Claritin, Allegra, Bilaxten and Zyrtec.

The medications listed above are over-the-counter antihistamines. When you take them, follow the manufacturer’s instructions and avoid overmedicating. Taking more than directed will not provide quicker or better results. It actually has the opposite effect, and impairs your abilities even more.

For severe symptoms, you may have your physician prescribe a stronger antihistamine. Taking these stronger medications may require a doctor’s note to excuse you from work, depending on what you do.

Always tell your supervisor when taking an antihistamine. It is better to be transparent about taking an antihistamine while at work than to risk a serious injury from the side effects.

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