What is hay fever?

Hay fever, or allergic rhinitis, is an allergic reaction to certain particles breathed in through the nose. Common symptoms include sneezing, itchy eyes and a blocked or runny nose. During spring and summer, symptoms are usually triggered by pollen from grasses, trees and weeds. In contrast, hay fever that occurs all year round is usually due to other airborne particles, such as mould, dust mites or animal hair.

Hay fever is an 'atopic' condition, meaning that it runs in families and tends to affect people with other related allergic conditions, such as asthma and eczema. In each of these conditions, the immune system attacks healthy cells by mistake, as if fighting an infection. During hay fever, this allergic response causes inflammation and swelling in the nose, throat and eyes.

Allergies that cause hay fever are not present from birth. Instead, they occur after coming into contact with a particular substance on multiple occasions, a process known as 'sensitisation'. Although hay fever can occur at any age, sensitisation usually occurs before 10 years of age. After this point, hay fever may keep occurring each time the immune system detects the triggering substance.

While there's no cure for hay fever, the condition can generally be well controlled by avoiding triggers and taking one or more medications.

Immune system

The organs and cells involved in protecting the body against infection.

Causes

The nose and connecting airways are lined with a thin layer of mucus that traps foreign particles, such as pollen, dust and bacteria. Tiny hairs (cilia) in this layer help to sweep mucus to the back of the throat and down into the stomach. Hay fever occurs when particles trapped in the nose trigger an allergic reaction, also known as a type I hypersensitivity reaction.

During this reaction, the immune system produces an antibody called immunoglobulin E (IgE). In people without allergies, IgE is usually only released to help fight infections. However, if you have hay fever, IgE antibodies attach themselves to another kind of immune cell, known as mast cells. In turn, these mast cells release histamine and other chemicals when the IgE antibodies recognise foreign particles trapped in the nose.

Histamine causes fluid to leak from certain cells that line the nose, mouth, throat and eyes. The end result is inflammation and swelling, leading to the symptoms of hay fever.

Substances known to trigger hay fever or make symptoms worse in some people include:

  • Tree pollen;
  • Grass pollen;
  • Weed pollen;
  • Fungal spores  -  particularly from moulds or yeasts;
  • Dust, pollution, fumes or gases from certain chemicals, such as latex, adhesives, chlorine and formaldehyde;
  • Animal skin, hair or saliva (these are known collectively as dander);
  • Dust mites, and;
  • House dust.

Allergic reaction cycle showing: antibodies being produced in response to pollen; antibodies binding to a mast cell at the base and to pollen at the upper fork; an activated mast cell releasing histamine.Hay fever is the result of an immune response to allergens. 

Histamine

A type of compound found in all body cells. It has several roles in the body, being released by the tissues as an inflammatory response to an allergic reaction and playing a role in the function of nerves and the gut. In addition, the compound can be found in certain foods, such as cheese and wine, which when consumed can potentially induce allergic reactions.

Immune system

The organs and cells involved in protecting the body against infection.

Risk factors

Risk factors that increase the likelihood of developing hay fever include:

  • A personal or family history of hay fever, allergic reactions, eczema and/or asthma;
  • Regular exposure to allergens at home or work, and;
  • Exposure to tobacco smoke during early childhood.

Types

Hay fever is sometimes classified as 'seasonal' or 'perennial' depending on when symptoms occur.

Seasonal hay fever

As the name suggests, seasonal hay fever occurs mainly during spring, summer or early autumn, usually in response to increased levels of pollen in the air. Symptoms generally affect the nose, throat and eyes.

Perennial hay fever

Perennial hay fever occurs all year round and is usually triggered by substances found indoors, such as fungal spores, dust and animal dander (skin, hair and saliva). This type of hay fever usually produces a runny nose and sneezing, but rarely affects the eyes and throat.

Signs and symptoms

Hay fever symptoms can vary depending on the type of allergic reaction, weather conditions and level of pollen in the air. In general though, symptoms appear straight after exposure to a triggering allergen and may include:

  • Sneezing;
  • Itchy, red and watery eyes (allergic conjunctivitis);
  • A blocked or runny nose (rhinitis);
  • An itchy throat, nose and mouth;
  • A cough, caused by mucus dripping down the throat (postnasal drip);
  • Pain in the face, caused by blocked sinuses (sinusitis);
  • A reduced sense of smell;
  • Headache;
  • Earache, and;
  • Tiredness.

A man with red, watery eyes and inflammation of the nose, mouth and throat.Signs and symptoms of hay fever. 

Methods for diagnosis

Your doctor will usually diagnose hay fever by looking in your throat and nose and asking about symptoms. You may also be asked questions about your personal or family history of allergies.

In some cases, hay fever can be easily recognised and the cause identified without any tests. However, if further investigation is needed, your doctor may refer you for a specialised blood test. Also known as a radioallergosorbent test (RAST), this procedure can help to diagnose hay fever and other related allergic reactions by measuring the amount of IgE antibody in your blood.

If you have severe, persistent symptoms, a skin prick test or patch test may be necessary. These tests involve applying substances to the skin of the back or arms and then looking for signs of an allergic reaction.

A skin patch test is used to identify causes of allergic reactions. 

Types of treatment

For mild to moderate cases of hay fever, home-care measures and over-the-counter medications may work for you. However, for symptoms that are particularly uncomfortable or severe, one or more prescription medications may be needed.

Self care

If you have seasonal hay fever, it may be useful to monitor the daily pollen count, particularly during spring, summer and early autumn. The pollen count provides an average measure of pollen grains in one cubic metre of air. In general, the pollen count is lower on rainy days and higher when it's sunny, windy, late afternoon or early evening.

On days when the count is high, modifying your behaviour to avoid exposure to pollen may help to relieve or prevent symptoms. Similarly, if your hay fever is triggered by something other than pollen, avoiding these trigger substances may be an effective treatment.

Medications

Antihistamines

As a starting point, your doctor may suggest an over-the-counter antihistamine tablet or syrup. As the name suggests, antihistamines work by blocking the immune response that causes release of histamine into the nose, mouth, throat and eyes. Some examples of antihistamine medications include loratadine, fexofenadine and cetirizine.

Alternatively, you may be prescribed a 'sedating antihistamine' such as promethazine, cyproheptadine or diphenhydramine. As these medications also cause drowsiness, they may be recommended for use at night.

If your hay fever doesn't occur very often or only affects your nose, your doctor may suggest an antihistamine spray instead.

Antihistamines tend to work well against sneezing, itching and watery eyes, but may not help with a blocked nose. They may also be taken before hay fever develops, to reduce the severity of symptoms when they occur.

Decongestants

Decongestants may help to relieve a blocked or runny nose by reducing inflammation inside the nose and sinuses. Your doctor will most likely suggest an over-the-counter tablet form, to be taken alone or together with an antihistamine medication. Some examples of oral decongestant tablets include phenylephrine and pseudoephedrine. Side effects of these medications can include nervousness and trouble sleeping (insomnia).

Intranasal decongestant sprays are also available over the counter for short-term relief of hay fever symptoms. However, taking these medications for longer than five days or at a higher-than-recommended dose can make the nose blocked constantly unless the medication is used repeatedly. Also known as 'rebound congestion', this side effect can take weeks to improve. Nasal decongestants are not usually suitable for children under six years of age.

A man inhaling an intranasal decongestant spray through his nose.Intranasal decongestant spray can offer short-term relief of hay fever symptoms. 

Corticosteroids

If treatment with over-the-counter medications isn't successful, your doctor may prescribe a corticosteroid medication. These work by reducing inflammation in the nose and decreasing mucus production. For this reason, they may relieve itchy and watery eyes, but also tend to be more effective than antihistamines in treating a blocked or runny nose.

Some examples of corticosteroids that can be sprayed directly into the nose once or twice a day include triamcinolone acetonide, budesonide, fluticasone and mometasone. These sprays may also be used as a preventative measure a few weeks before symptoms are expected to begin. They tend to work best when used continuously over consecutive days, or even weeks.

If a spray is not effective, your doctor may prescribe an oral corticosteroid tablet, such as prednisolone. When swallowed, these medications circulate in the blood to produce a strong and rapid response, rather than just reaching the nose.

However, oral corticosteroids are not usually prescribed for more than two weeks as long-term side effects can include high blood pressure (hypertension), eye problems, thinning of the skin and weight gain.

Other nasal sprays

Flushing the nose with salt water several times a day may also help to clear a blocked nose. Salt water sprays are available over the counter, or may be prepared at home.

Another over-the-counter medication, sodium cromoglycate, is thought to work by preventing mast cells from releasing inflammatory histamine. It is usually taken up to five times a day and works best when taken on several consecutive days to build up an effect.

In contrast, ipratropium may be prescribed if your main symptom is a very runny nose. However, it will have no effect on a blocked nose or sneezing.

Consulting your doctor for advice on how to prepare and use these nasal sprays is recommended.

Eye drops

For itchy or sore eyes, your doctor may suggest an over-the-counter eye medication containing an antihistamine, corticosteroid or sodium cromoglycate. Possible side effects from some eye drops can include a stinging or burning sensation in the eyes.

Immunotherapy

Also known as 'desensitisation', this treatment involves regular injections or oral doses of a particular substance known to produce hay fever, in order to build up a resistance to it. The amount of substance given each time is increased gradually, and treatment usually continues over a number of years. In some people, the overall immune response decreases, leading to an improvement in hay fever symptoms.

Immunotherapy is usually arranged by an allergy specialist and then administered by your general practitioner. Immunotherapy is usually only recommended when symptoms are severe or other treatments have not worked.

Leukotriene inhibitors

For children who have hay fever as well as asthma, your doctor may prescribe a leukotriene inhibitor tablet. Medications from this family are most commonly prescribed for asthma alone, but they can also help to clear a runny or blocked nose. Some examples of leukotriene inhibitor medications prescribed for hay fever include montelukast and zileuton.

Histamine

A type of compound found in all body cells. It has several roles in the body, being released by the tissues as an inflammatory response to an allergic reaction and playing a role in the function of nerves and the gut. In addition, the compound can be found in certain foods, such as cheese and wine, which when consumed can potentially induce allergic reactions.

Potential complications

Potential complications of hay fever include:

  • Infection, starting in the trapped mucus and spreading to the sinuses (sinusitis) or ears (middle ear infection);
  • Disruptions to daily life, including absences from work or school, poor sleep patterns, tiredness, reduced concentration and headaches;
  • Growths inside the nose (nasal polyps);
  • Triggering of other allergic conditions, such as eczema and asthma;
  • Worsening of asthma symptoms;
  • Development of new allergies, and;
  • A severe allergic reaction (anaphylaxis).

Nasal polyps

Fleshy outgrowths or lumps from the internal lining of the nose and sinus, often due to allergies, that can cause nasal obstruction and sinusitis.

Prognosis

Although there's no cure or vaccination for hay fever, some children do outgrow the condition over time. It's also possible for hay fever to clear for an extended period and then return later in life.

In many cases though, hay fever is a lifelong condition and symptoms return with each new exposure to a triggering substance. However, the outlook for hay fever is generally good when the condition is controlled with a combination of self-care measures and medications.

Prevention

While it is not possible to prevent hay fever, symptoms can be controlled by modifying your behaviour and avoiding exposure to triggering substances. 

In cases where hay fever symptoms occur all year round and are not caused by pollen, some possible measures could include dusting frequently, removing household items that collect dust and washing soft furnishings regularly in hot water. Avoiding cigarette smoke, keeping animals outside and doing household repairs to eliminate mould might also help to prevent or reduce symptoms.