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Reasons to Have One, What to Expect, Associated Risks & More

3 Reasons You Would Need Antihistamines

1. Manage Allergy Symptoms

Antihistamines can be taken every day to help manage and keep allergy symptoms under control.[1] If you are regularly exposed to allergens in your daily environment at work, school, or at home, antihistamines may help prevent your symptoms from flaring or worsening. Examples of common allergens you may be exposed to on a daily basis include pollen, dust, and pet dander.[2]

2. Relieve Allergy Symptoms

Antihistamines can be used to treat allergy symptoms the moment they arise.[1] For example, if you visit someone who owns dogs and has pet dander in their home, you can take antihistamines to reduce your symptoms and find relief.

3. Prevent Allergy Symptoms

Antihistamines can be used to prevent or reduce allergy symptoms before you expose yourself to known triggers and allergens.[1] For example, if you’re allergic to pollen and plan on spending time outdoors when pollen counts are higher than usual, antihistamines may help prevent or reduce your symptoms. Antihistamines can also be taken at bedtime to prevent allergy symptoms from setting in between the hours of 4 a.m. and 6 a.m., which is when symptoms are usually at their worst.[1]

Understanding Antihistamines

Antihistamines are medicines used to treat allergy symptoms. Allergies are responses and reactions to substances that are not usually considered harmful, such as dust, pet dander, pollen, and certain foods like nuts and shellfish.[2] Antihistamines work by blocking the effects of histamines, which are natural chemicals released by the body in response to substances it considers harmful.

Antihistamines can treat common allergy symptoms including hives, skin rashes, congestion, runny nose, tearing eyes, sneezing, itching, and swelling of the nasal passages. Antihistamines may also treat dizziness, nausea, vertigo, cough, and anaphylaxis.[3] These medicines are available in the form of pills, capsules, chewable tablets, eye drops, injections, and liquids.[2]

Antihistamines can work for as long as anywhere between 4 and 24 hours depending on the types and dosage. Some antihistamines are combined with a decongestant to dry up the nasal passages and relieve runny nose, while others may cause drowsiness to help you experience relief from all other symptoms.[1] Your doctor can work with you to choose an antihistamine that works best based on your allergy triggers, symptoms, and lifestyle.

Risks of Antihistamines

Antihistamines may cause side effects including dry mouth, dry throat, blurry vision, dizziness, drowsiness, impaired motor function, loss of appetite, urinary retention, constipation, and feelings of nervousness, excitement, and/or irritability.[1] These side effects can lead to dangerous outcomes for those who don’t take the necessary precautions when using these drugs. For instance, blurry vision, dizziness, and drowsiness can impair one’s ability to operate vehicles to increase the risk of an accident.[4]

Antihistamines may worsen urinary retention and narrow-angle glaucoma. These medicines may also cause liver injury, though this is rare. Antihistamines that are most commonly linked to liver injury are cyproheptadine and cetirizine.[3]

Take note of the side effects you experience when using antihistamines, and talk to your doctor about alternative treatments if certain side effects put you at risk or interfere with your ability to perform normal daily activities. If switching to another medication or treatment isn’t an option, make plans to avoid doing certain activities that can put you at risk when using antihistamines.

What to Expect with Antihistamines

Antihistamines will help reduce and/or relieve your allergy symptoms. Each antihistamine works differently from the next and takes a certain amount of time to produce effects. Read the labels on all antihistamine drugs before using them and take as directed. Familiarize yourself with the side effects so you know exactly what to expect, and whether it’s safe to perform activities such as driving a car or operating machinery when using that particular antihistamine.[4] Avoid using alcohol, sedatives, and tranquilizers when using antihistamines, since these substances may increase drowsiness.

Questions to Ask Your Doctor About Antihistamines

  • Are antihistamines my only option for relief from allergy symptoms?
  • Can I use over-the-counter antihistamines, or do I need prescription antihistamines?
  • Which type of antihistamine is best for treating my symptoms?
  • What are the most common side effects of the antihistamines I’m using?
  • Should I avoid the use of certain foods, drinks, or substances while using antihistamines?
  • Are there any activities I should avoid while using antihistamines?
  • Will I need to use antihistamines for life to treat my allergies?
  • Can I use antihistamines that won’t cause drowsiness?
  • Is it safe to use antihistamines if I am pregnant or breastfeeding?
  • Can I use antihistamines proactively to avoid allergy symptoms?

Antihistamines May Also be Known as:

  • Allergy medicines
  • Allergy shots
  • Allergy drugs
  • Allergy medications
  • Histamine blockers
  • Allergy pills
  • Allergy tablets
  • Oral antihistamines



Solv has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.

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