Switch Language

Allergy Basics

From fluffy kittens to lush lawns to shady trees, some of the most beautiful things out there can make allergy symptoms act up. Find out what causes allergies and what to do about them, so you can enjoy more of the world around you.

What Are Allergies?

In people with allergies, the immune system mistakes a substance that’s ordinarily harmless to most people (substances from pollen , mould , pet dander and dust mites ) for something dangerous and attacks it. These normally harmless substances are called allergens.

an outline of a cloud

What Causes Allergy Symptoms?

When you take a breath or rub your nose or eyes, allergens enter your body and your immune system and trigger a hypersensitivity reaction. To get rid of the substance it thinks is harmful, your body undergoes various reactions and releases inflammatory mediators like histamine .

When the histamine binds to receptors on other cells in your body, it causes you to experience allergy symptoms, including runny nose, sneezing, itchy/watery eyes or itchy nose.

Outlined lightbulb with rays of light


To rid itself of the allergen , your body undergoes various allergic reactions known as the “allergic cascade.”1 This results in various inflammatory mediators. One of these mediators that is released by the immune system after being exposed to an allergen is histamine . When you inhale an allergen, mast cells release histamine. Histamine then attaches to receptors on nearby blood vessels, causing them to enlarge (dilate). Histamine also binds to other receptors located in nasal tissues, causing swelling, itching and runny nose.

an outline of a cloud

How Claritin® Helps Reduce Allergy Symptoms

a flower bouqet with, "there are over 200 different allergens out there," superimposed on top


Claritin® is an antihistamine so it hinders the cascade triggered by allergens.

an outline of a cloud

How Are Allergies Diagnosed?

Sometimes, it’s easy to guess what you might be allergic to. For example, do you sneeze every time you go into a dusty attic? Or do your symptoms act up every year during ragweed season?

But if you’re not sure what’s causing your symptoms, you can see an allergist to help identify what you’re allergic to — so you know what triggers to avoid. At the appointment, your doctor will:1

  • Take your personal and medical history to help understand your symptoms and their possible causes. It’s a good idea to jot down some notes before your appointment about your family history, lifestyle and potential triggers.
  • Perform a physical exam, paying special attention to your nose, throat, eyes, ears, chest and skin.
  • Conduct a skin test, patch test and/or blood test to help determine what you’re allergic to.
an outline of a cloud

Reducing Your Exposure to Airborne Allergens

In addition to taking Claritin® to relieve symptoms, it’s important to help reduce your exposure to allergy triggers in the first place. You can find simple tips for helping to reduce your exposure to the different indoor and outdoor allergens below.

Outdoor Seasonal Allergies

Outdoor allergies are often called seasonal allergies because they change with the seasons. They’re caused by an overreaction of the immune system to ordinarily harmless allergens found outside, such as mould spores and tree, grass and weed pollens. While these allergens can be difficult to avoid, you can find easy tips to help minimize your exposure so you can enjoy more of the great outdoors.


Indoor Allergies

Indoor allergies are caused by an overreaction of the immune system to allergens from dust mites , pet dander and mould. Indoor allergies can happen any time of the year, but may be more troublesome in the winter when many people spend more time inside. Our simple tips can help you reduce allergy triggers in your home.



  1. Allergy Diagnosis. Asthma and Allergy Foundation of America. Accessed November 30, 2017.


A box of Claritin Allergy

Claritin® Tablets - 24HR

One non-drowsy tablet quickly and effectively relieves allergy symptoms all day. For ages 12+

Claritin® Allergy + Sinus - 12HR

Claritin® Allergy + Sinus - 12HR

This effective tablet relieves allergy symptoms, sinus and nasal congestion for 12 hours. For ages 12+

Claritin® Allergy + Sinus Extra Strength - 24HR

Claritin® Allergy + Sinus Extra Strength - 24HR

One non-drowsy caplet effectively relieves allergy symptoms and nasal congestion, all day. For ages 12+