Hay fever, also known as allergic rhinitis, occurs when the immune system overreacts to allergens such as pollen, dust mites, mold or animal dander. The reaction can cause sneezing, a runny or blocked nose, itchy or watery eyes and other symptoms.
Despite its name, hay fever is not caused by hay and does not always occur during a particular season. Symptoms can occur throughout the year, depending on the allergen involved.
The condition develops when the immune system identifies a normally harmless substance as a threat. In people with allergies, exposure to an allergen can trigger the production of immunoglobulin E (IgE) antibodies. This leads to the release of histamine and other chemicals that cause inflammation and allergy symptoms.
Symptoms
Common symptoms of hay fever include:
- Sneezing
- A runny or blocked nose
- Itchy, red or watery eyes
- Itchy throat, nose or ears
- Coughing
- Post-nasal drip
- Sinus pressure or a mild headache
Symptoms vary from person to person and can depend on the allergen and level of exposure.
Some people with allergic rhinitis also have asthma. Allergens can worsen asthma symptoms, including wheezing, chest tightness and difficulty breathing. People experiencing breathing problems should seek medical advice rather than assuming the symptoms are caused only by hay fever.
What causes hay fever?
Pollen is one of the main triggers of seasonal allergic rhinitis. Depending on the region and time of year, pollen can come from trees, grasses and weeds.
Other allergens can cause symptoms throughout the year. They include:
Dust mites: These microscopic organisms commonly live in bedding, carpets and upholstered furniture. Their waste and body particles can trigger allergic reactions.
Mold: Mold releases spores into the air that can cause allergic symptoms when inhaled.
Pet allergens: Cats, dogs and other animals can expose people to proteins found in skin flakes, saliva and other substances. These are commonly referred to as pet dander.
Environmental irritants such as smoke and strong odors can also worsen nasal symptoms, although they do not necessarily cause an allergic reaction.
Food allergies are different from hay fever and should not generally be described as a cause of allergic rhinitis. Some people with pollen allergies can, however, experience an itchy mouth or throat after eating certain raw fruits or vegetables because of a condition known as pollen-food allergy syndrome.
Who is more likely to develop hay fever?
A family history of allergies or asthma can increase a person’s likelihood of developing allergic rhinitis. People who already have another allergic condition may also be at greater risk.
Exposure to particular allergens also varies according to where a person lives, works and spends time. Pollen levels, for example, can differ substantially between regions and seasons.
Hay fever is not limited to children or older adults, and there is no reliable basis for the claim that simply being older makes a person more likely to develop pollen allergies.
Hay fever and post-nasal drip
Post-nasal drip occurs when mucus from the nose or sinuses drains down the back of the throat. Allergic rhinitis can cause it because inflammation in the nasal passages increases mucus production.
Infections such as the common cold can also cause post-nasal drip. Other possible causes include sinus problems and exposure to environmental irritants.
The sensation can include frequent throat clearing, coughing or a feeling of mucus at the back of the throat. Identifying the underlying cause is important because treatment depends on what is producing the symptoms.
Treatment and when to seek help
Treatment for hay fever depends on the severity of symptoms and the trigger. Avoiding known allergens can help, while medicines such as antihistamines and certain nasal sprays may reduce symptoms.
If symptoms persist, interfere with daily activities or do not improve with usual treatment, a doctor or allergy specialist can help determine whether allergic rhinitis is responsible and identify possible triggers.
Anyone experiencing significant difficulty breathing, severe wheezing or other serious symptoms should seek medical attention promptly.
