December 2, 2022

Antihistamine – Types, Side Effects and Precautions

By blocking the effects of histamine, this class of drugs can treat allergies and many other ailments.

An antihistamine is a type of medicine used to treat common allergy symptoms, such as sneezing, watery eyes, hives, and runny nose.

According to the American College of Allergy, Asthma, & Immunology, nasal allergies affect approximately 50 million people in the United States.

Certain antihistamines are also sometimes used to treat motion sickness, nausea, vomiting, dizziness, cough, trouble sleeping, anxiety, and Parkinson’s disease.

The drugs work by blocking the effects of histamine, a substance in the body that can cause allergy symptoms.

Antihistamines come in different forms, such as capsules, tablets, liquids, eye drops, injections, and nasal sprays.

They can be purchased over-the-counter (OTC) or dispensed with a prescription.

Some antihistamines are taken daily, while others are only used when symptoms appear.

Types of antihistamines

Some common antihistamines include:

Side effects of antihistamines

Common side effects of antihistamines include:

  • Drowsiness or drowsiness
  • Dizziness
  • Dry mouth, nose or throat
  • Increased appetite and weight gain
  • Stomach ache
  • Thickening of mucus
  • Vision changes
  • Feeling nervous, excited, or irritable

Antihistamine precautions

Before taking an antihistamine, tell your doctor about any medical conditions you have, especially:

Do not drive or do activities that require mental alertness until you know how the antihistamine you are taking affects you.

Follow the directions on your prescription or package label carefully when taking an antihistamine. Do not take more medicine than recommended.

Tell your doctor about all prescription, non-prescription, illegal, recreational, herbal, nutritional, or dietary medications you are taking before starting an antihistamine.

You may need to avoid grapefruit and grapefruit juice while taking an antihistamine because they can affect how these drugs work in your body. Speak to your doctor if this concerns you.

Antihistamines and alcohol

Alcohol can make some side effects of antihistamines worse.

Avoid drinking alcohol while taking these medications.

Antihistamines and pregnancy

Tell your doctor if you are pregnant or could become pregnant while using an antihistamine.

You will need to discuss the risks and benefits of taking the drug during pregnancy.

Also talk to your health care provider before taking antihistamines if you are breastfeeding.