July 05, 2019

Antihistamine Medications: How Do They Work?

How Do Antihistamines Work?

Most people have heard the name but can’t necessarily provide a detailed answer to the question, “What is an antihistamine?”. Antihistamines are medications used to prevent or treat allergy symptoms. While all physicians can explain the need for antihistamines, allergists, who are doctors specializing in the treatment of allergies, can provide in-depth information about these medications.

What Symptoms Do Antihistamines Treat?

Antihistamines have a wide range of uses. They’re most frequently prescribed to treat common allergy symptoms, including:

  • Sneezing
  • Runny nose
  • Watery eyes
  • Hives (small, pale red bumps, called plaques, on the skin)

However, in addition to the use of antihistamines for allergic reactions, they may also be prescribed to treat:

  • Motion sickness
  • Dizziness
  • Nausea
  • Vomiting
  • Stiffness and shaking caused by Parkinson’s disease
  • Anxiety
  • Sleeplessness

People who have an allergy component of their condition may also take antihistamines for asthma.

How Do Antihistamines Work?

Patients who’ve been prescribed this type of medication may wonder, “How do antihistamines work?”. The answer is that the body responds to allergens by producing histamines, chemicals that cause the symptoms you experience when you’re exposed to an allergy trigger. Antihistamines block the effect of histamines, preventing or reducing the allergic reaction. How long do antihistamines take to work? That depends on a number of factors, including how much exposure you’ve had to the allergen.

Are There Different Types of Antihistamines?

What are the different types of antihistamines? They come in many forms. This includes tablets and capsules that are appropriate for older children and adults; and liquids, which make it easier for children to take. Antihistamines also come in nasal sprays and eyedrops. Some antihistamines are available in the cold/allergy aisle at the pharmacy, while others require a prescription.

Patients will sometimes ask, “What’s the most effective over-the-counter antihistamine?”. That depends on each person’s trigger allergen or allergens. By making an appointment with a Baptist Health allergist, you can learn more about your allergies and how to treat them.

What Are the Common Short- and Long-Term Side Effects of Antihistamines?

Antihistamines are generally safe. However, as with any medication, there are potential side effects of both short- and long-term use.

Short-Term Side Effects of Antihistamines

Side effects may include:

  • Sleepiness
  • Irritability, excitability or nervousness
  • Dizziness
  • Stomach upset
  • Dryness of the nose, mouth or throat
  • Increased appetite
  • Thicker mucus
  • Vision changes

Long-Term Side Effects of Antihistamines

Potential harmful effects of antihistamines, when taken for a long period include:

  • Weight gain
  • Diabetes
  • High blood pressure
  • Sleep issues
  • Memory loss
  • Mood issues
  • Osteoporosis

Are There Any Precautions to Take with Antihistamines?

Certain precautions should be followed by antihistamines. You should let your doctor know if you’re pregnant or might become pregnant, as taking an antihistamine during pregnancy may not be advised. You should also tell your doctor if you’re breastfeeding.

As far as interactions with other substances, can you drink alcohol after taking antihistamines? You shouldn’t, as alcohol can worsen some antihistamine side effects.

You should also talk with your doctor before taking antihistamines if you have certain medical conditions, including:

  • Heart disease
  • High blood pressure
  • Epilepsy
  • Diabetes
  • An overactive thyroid
  • Glaucoma
  • An enlarged prostate
  • Trouble urinating

Finally, you shouldn’t drive or take part in activities that require you to be mentally alert until you understand how your antihistamine affects you.

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