Allergic rhinitis is caused by an allergic reaction to an allergen, such as pollen, dust and certain animals.

Oversensitive immune system

If you have allergic rhinitis, your natural defence against infection and illness (your immune system) will react to an allergen as if it were harmful.

If your immune system is oversensitive, it'll react to allergens by producing antibodies to fight them off.

Antibodies are special proteins in the blood that are usually produced to fight viruses and infections.

Allergic reactions do not happen the first time you come into contact with an allergen.

The immune system has to recognise and "memorise" it before producing antibodies to fight it. This process is known as sensitisation.

After you develop sensitivity to an allergen, it'll be detected by antibodies called immunoglobulin E (IgE) whenever it comes into contact with the inside of your nose and throat.

These antibodies cause cells to release a number of chemicals, including histamine, which can cause the inside layer of your nose (the mucous membrane) to become inflamed and produce too much mucus.

This is what causes the typical symptoms of sneezing and a blocked or runny nose.

Common allergens

Allergic rhinitis is triggered by breathing in tiny particles of allergens. The most common airborne allergens that cause rhinitis are dust mites, pollen and spores, and animal skin, urine and saliva.

House dust mites

House dust mites are tiny insects that feed on the dead flakes of human skin. They can be found in mattresses, carpets, soft furniture, pillows and beds.

Rhinitis is not caused by the dust mites themselves, but by a chemical found in their excrement.

Dust mites are present all year round, although their numbers tend to peak during the winter.

Pollen and spores

Tiny particles of pollen produced by trees and grasses can sometimes cause allergic rhinitis.

Most trees pollinate from early to mid-spring, whereas grasses pollinate at the end of spring and beginning of summer.

Rhinitis can also be caused by spores produced by mould and fungi.

Animals

Many people are allergic to animals, such as cats and dogs. The allergic reaction is not caused by animal fur, but flakes of dead animal skin and their urine and saliva.

Dogs and cats are the most common animals to cause allergies, although some people are affected by horses, cattle, rabbits and rodents, such as guinea pigs and hamsters.

But being around dogs from an early age can help protect against allergies, and there's some evidence to suggest that this might also be the case with cats.

Work-related allergens

Some people are affected by allergens found in their work environment, such as wood dust, flour dust or latex.

Who's most at risk

It's not fully understood why some people become oversensitive to allergens, although you're more likely to develop an allergy if there's a history of allergies in your family.

If this is the case, you're said to be "atopic", or to have "atopy". People who are atopic have a genetic tendency to develop allergic conditions.

Their increased immune response to allergens results in increased production of IgE antibodies. 

Environmental factors may also play a part. Studies have shown certain things may increase the chance of a child developing allergies, such as growing up in a house where people smoke and being exposed to dust mites at a young age.

Your GP will often be able to diagnose allergic rhinitis from your symptoms and your personal and family medical history.

They'll ask you whether you have noticed any triggers that seem to cause a reaction, and whether it happens at a particular place or time.

Your GP may examine the inside of your nose to check for nasal polyps.

Nasal polyps are fleshy swellings that grow from the lining of your nose or sinuses, the small cavities inside your nose.

They can be caused by the inflammation that occurs as a result of allergic rhinitis.

Allergic rhinitis is usually confirmed when medical treatment starts. If you respond well to antihistamines, it's almost certain that your symptoms are caused by an allergy.

Allergy testing

If the exact cause of allergic rhinitis is uncertain, your GP may refer you to a hospital allergy clinic for allergy testing.

The 2 main allergy tests are:

• a skin prick test – where the allergen is placed on your arm and the surface of the skin is pricked with a needle to introduce the allergen to your immune system; if you're allergic to the substance, a small itchy spot (welt) will appear
• a blood test – to check for the immunoglobulin E (IgE) antibody in your blood; your immune system produces this antibody in response to a suspected allergen

Commercial allergy testing kits are not recommended because the testing is often of a lower standard than that provided by the NHS or an accredited private clinic.

It's also important that the test results are interpreted by a qualified healthcare professional with detailed knowledge of your symptoms and medical history.

Further tests

In some cases further hospital tests may be needed to check for complications, such as nasal polyps or sinusitis.

For example, you may need:

• a nasal endoscopy – where a thin tube with a light source and video camera at 1 end (endoscope) is inserted up your nose so your doctor can see inside your nose
• a nasal inspiratory flow test – where a small device is placed over your mouth and nose to measure the air flow when you inhale through your nose
• a CT scan – a scan that uses X-rays and a computer to create detailed images of the inside of the body

Treatment for allergic rhinitis depends on how severe your symptoms are and how much they're affecting your everyday activities.

In most cases treatment aims to relieve symptoms, such as sneezing and a blocked or runny nose.

If you have mild allergic rhinitis, you can often treat the symptoms yourself. 

You should visit your GP if your symptoms are more severe and affecting your quality of life, or if self-help measures have not worked.

Self-help

It's possible to treat the symptoms of mild allergic rhinitis with medicines you buy from a pharmacy or shop, such as long-acting non-sedating antihistamines.

If possible, try to reduce exposure to the allergen that triggers the condition.

Find out more about preventing allergic rhinitis

Cleaning your nasal passages

Regularly cleaning your nasal passages with a salt water solution, known as nasal douching or irrigation, can also help by keeping your nose free of irritants.

You can do this by using a solution made with sachets bought from a pharmacy.

Small syringes or pots that often look like small horns or teapots are also available to help flush the solution around the inside of your nose.

To rinse your nose:

• stand over a sink, cup the palm of 1 hand and pour a small amount of the solution into it
• sniff the water into 1 nostril at a time
• repeat this until your nose feels comfortable (you may not need to use all of the solution)

While you do this, some solution may pass into your throat through the back of your nose.

The solution is harmless if swallowed, but try to spit out as much of it as possible.

Nasal irrigation can be carried out as often as necessary, but a fresh solution should be made each time.

Medication

Medication will not cure your allergy, but it can be used to treat the common symptoms.

If your symptoms are caused by seasonal allergens, such as pollen, you should be able to stop taking your medication after the risk of exposure has passed.

Visit your GP if your symptoms do not respond to medication after 2 weeks.

Antihistamines

Antihistamines relieve symptoms of allergic rhinitis by blocking the action of a chemical called histamine, which the body releases when it thinks it's under attack from an allergen.

You can buy antihistamine tablets from your pharmacist without a prescription, but antihistamine nasal sprays are only available with a prescription.

Antihistamines can sometimes cause drowsiness. If you're taking them for the first time, see how you react to them before driving or operating heavy machinery.

In particular, antihistamines can cause drowsiness if you drink alcohol while taking them.

Corticosteroids

If you have frequent or persistent symptoms and you have a nasal blockage or nasal polyps, your GP may recommend a nasal spray or drops containing corticosteroids.

Corticosteroids help reduce inflammation and swelling. They take longer to work than antihistamines, but their effects last longer.

Side effects from inhaled corticosteroids are rare, but can include nasal dryness, irritation and nosebleeds.

If you have a particularly severe bout of symptoms and need rapid relief, your GP may prescribe a short course of corticosteroid tablets lasting 5 to 10 days.

Add-on treatments

If allergic rhinitis does not respond to treatment, your GP may choose to add to your original treatment. 

They may suggest:

• increasing the dose of your corticosteroid nasal spray
• using a short-term course of a decongestant nasal spray to take with your other medication
• combining antihistamine tablets with corticosteroid nasal sprays, and possibly decongestants
• using a nasal spray that contains a medicine called ipratropium, which will help reduce nasal discharge and make breathing easier
• using a leukotriene receptor antagonist medication, which blocks the effects of chemicals called leukotrienes that are released during an allergic reaction

If you do not respond to the add-on treatments, you may be referred to a specialist for further assessment and treatment.

Immunotherapy

Immunotherapy, also known as hyposensitisation or desensitisation, is another type of treatment used for some allergies.

It's only suitable for people with certain types of allergies, such as hay fever, and is usually only considered if your symptoms are severe.

Immunotherapy involves gradually introducing more and more of the allergen into your body to make your immune system less sensitive to it.

The allergen is often injected under the skin of your upper arm. Injections are given at weekly intervals, with a slightly increased dose each time.

Immunotherapy can also be carried out using tablets that contain an allergen, such as grass pollen, which are placed under your tongue.

When a dose is reached that's effective in reducing your allergic reaction (the maintenance dose), you'll need to continue with the injections or tablets for up to 3 years.

Immunotherapy should only be carried out under the close supervision of a specially trained doctor, as there's a risk it may cause a serious allergic reaction.

If you have allergic rhinitis, there's a risk you could develop further problems.

A blocked or runny nose can result in difficulty sleeping, drowsiness during the daytime, irritability and problems concentrating.

Allergic rhinitis can also make symptoms of asthma worse.

The inflammation associated with allergic rhinitis can also sometimes lead to other conditions, such as nasal polyps, sinusitis and middle ear infections.

Nasal polyps

Nasal polyps are swellings that grow in the lining inside your nose or sinuses, the small cavities above and behind your nose.

They're caused by inflammation of the membranes of the nose and sometimes develop as a result of rhinitis.

Nasal polyps are shaped like teardrops when they're growing and look like a grape on a stem when fully grown.

They vary in size and can be yellow, grey or pink. They can grow on their own or in clusters, and usually affect both nostrils.

If nasal polyps grow large enough, or in clusters, they can interfere with your breathing, reduce your sense of smell and block your sinuses, which can lead to sinusitis.

Small nasal polyps can be shrunk using steroid nasal sprays so they do not cause an obstruction in your nose. Large polyps may need to be surgically removed.

Find out more about treating nasal polyps

Sinusitis

Sinusitis is a common complication of rhinitis. It's where the sinuses become inflamed or infected.

The sinuses naturally produce mucus, which usually drains into your nose through small channels.

But if the drainage channels are inflamed or blocked (for example, because of rhinitis or nasal polyps), the mucus cannot drain away and may become infected.

Common symptoms of sinusitis include:

• a blocked nose, making it difficult to breathe through your nose
• a runny nose
• mucus that drips from the back of your nose down your throat
• a reduced sense of smell or taste
• a feeling of fullness, pressure or pain in the face 
• snoring
• your airways becoming temporarily blocked while you're asleep, which can disturb your sleep (obstructive sleep apnoea)

Painkillers, such as paracetamol, ibuprofen or aspirin, can be used to help reduce any pain and discomfort in your face.

But these medications are not suitable for everyone, so check the leaflet that comes with them before using them.

For example, children under the age of 16 should not take aspirin, and ibuprofen is not recommended for people with asthma or a history of stomach ulcers. Speak to a GP or pharmacist if you're unsure.

Antibiotics may also be recommended if your sinuses become infected with bacteria.

If you have long-term sinusitis, surgery may be needed to improve the drainage of your sinuses.

Find out more about treating sinusitis

Middle ear infections

Middle ear infections can also develop as a complication of nasal problems, including allergic rhinitis.

These infections can occur if rhinitis causes a problem with the Eustachian tube, which connects the back of the nose and middle ear, at the back of the nose.

If this tube does not function properly, fluid can build up in the middle ear behind the ear drum and become infected.

There's also the possibility of infection at the back of the nose spreading to the ear through the Eustachian tube.

The main symptoms of a middle ear infection include:

• earache
• a high temperature
• being sick
• a lack of energy
• slight hearing loss

Ear infections often clear up within a couple of days, but paracetamol or ibuprofen can be used to help relieve fever and pain.

Antibiotics may also be prescribed if the symptoms persist or are particularly severe.

Find out more about treating middle ear infections

The best way to prevent allergic rhinitis is to avoid the allergen that causes it.

But this is not always easy. Allergens, such as dust mites, are not always easy to spot and can breed in even the cleanest house.

It can also be difficult to avoid coming into contact with pets, particularly if they belong to friends and family.

Below is some advice to help you avoid the most common allergens.

House dust mites

Dust mites are one of the biggest causes of allergies. They're microscopic insects that breed in household dust.

To help limit the number of mites in your house, you should:

• consider buying allergy-proof covers for mattresses, duvets and pillows
• choose wood or hard vinyl floor coverings instead of carpet
• fit roller blinds that can be easily wiped clean
• regularly clean cushions, soft toys, curtains and upholstered furniture, either by washing or vacuuming them
• use synthetic pillows and acrylic duvets instead of woollen blankets or feather bedding
• use a vacuum cleaner fitted with a high-efficiency particulate air (HEPA) filter – it can remove more dust than ordinary vacuum cleaners
• use a clean damp cloth to wipe surfaces – dry dusting can spread allergens further

Concentrate your efforts on controlling dust mites in the areas of your home where you spend most time, such as the bedroom and living room.

Pets

It's not pet fur that causes an allergic reaction, but exposure to flakes of their dead skin, saliva and dried urine.

If you cannot permanently remove a pet from the house, you may find the following tips useful:

• keep pets outside as much as possible or limit them to 1 room, preferably one without carpet
• do not allow pets in bedrooms
• wash pets at least once a fortnight
• groom dogs regularly outside
• regularly wash bedding and soft furnishings your pet has been on

If you're visiting a friend or relative with a pet, ask them not to dust or vacuum on the day you're visiting because it'll disturb allergens into the air.

Taking an antihistamine medicine 1 hour before you enter a house with a pet can help reduce your symptoms.

Pollen

Different plants and trees pollinate at different times of the year, so when you get allergic rhinitis will depend on what sort of pollens you're allergic to.

Most people are affected during the spring and summer months because this is when most trees and plants pollinate.

To avoid exposure to pollen, you may find the following tips useful:

• check weather reports for the pollen count and stay indoors when it's high
• avoid line-drying clothes and bedding when the pollen count is high
• wear wraparound sunglasses to protect your eyes from pollen
• keep doors and windows shut during mid-morning and early evening, when there's most pollen in the air
• shower, wash your hair and change your clothes after being outside
• avoid grassy areas, such as parks and fields, when possible 
• if you have a lawn, consider asking someone else to cut the grass for you

Mould spores

Moulds can grow on any decaying matter, both in and outside the house. The moulds themselves are not allergens, but the spores they release are.

Spores are released when there's a sudden rise in temperature in a moist environment, such as when central heating is turned on in a damp house or wet clothes are dried next to a fireplace.

To help prevent mould spores, you should:

• keep your home dry and well ventilated
• when showering or cooking, open windows but keep internal doors closed to prevent damp air spreading through the house, and use extractor fans
• avoid drying clothes indoors, storing clothes in damp cupboards and packing clothes too tightly in wardrobes
• deal with any damp and condensation in your home

Read more about how damp and mould can affect your health and how to get rid of damp and mould.