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What Causes Allergies?

All of us are exposed to different potential allergens at different times of the day. For example, if you go out to work and show allergy symptoms during the working day then something in your work environment may be triggering your allergy. Working out what causes allergies is the first step to finding the right treatment for you.


causes of hay fever

Hay fever season: causes of hay fever

Hay fever seasons vary from year to year but the spring and summer months are when people most commonly suffer from allergies to the different types of pollen — like weed and grass — and even mould spores.

Tree pollen normally occurs during spring. Grass and weed pollen occur during summer.


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The calendar shows the general pollen situation in the UK. The exact timing and severity of pollen seasons will differ from year to year depending on the weather and also regionally depending on geographical location.

Information supplied by the National Pollen and Aerobiology Research Unit. University of Worcester.

Coping with the hay fever season: how to prevent symptoms

Although this can be difficult in summer, keeping doors and windows shut helps prevent the flow of pollen throughout the house. It is also a good idea to have a shower, wash your hair and change your clothes after being outside as pollen will remain on your clothes and hair which can cause further irritation.

Try to avoid cutting the grass or ask a non-hay fever sufferer to do it instead, as grass pollen can trigger hay fever.


causes-pet allergies

What causes pet allergies?

Pets are also a common trigger for people's allergies. Cats, in particular, cause allergies but dogs and rabbits too can trigger the itching and sneezing of airborne allergy.

For most people, it is not the fur itself that causes the allergy problem. Dander, the name given to the mixture of small particles of fur, skin scales (like dandruff) and saliva, is the actual cause. In cats, for example, a particular protein found in cats' saliva causes an allergic reaction in many sufferers of airborne allergy. Because cats groom themselves so thoroughly, the saliva finds its way onto carpets, furniture and other surfaces.

Coping with pet & dander allergies

Keeping pets out of the bedroom helps reduce exposure.

Regular bathing of the animal can reduce the allergic problem by removing the saliva and dander that are the actual triggers.

For most people, the only way to reduce this problem is, sadly, to find a new home for their furry friend.

House dust mites

causes-dust mite allergy

What causes dust mite allergy?

It's not dust that triggers the problem. In fact, it is a tiny creature called the house dust mite, also known as Dermatophagoides pteronyssinus. House dust mites are almost always present in house dust, even in the most clean and tidy homes. Its first name 'Dermatophagoides' is simply Latin for 'skin eating'.

These microscopic creatures live in carpets, mattresses and upholstered furniture in homes and offices. They thrive in warm, humid climates. They eat dead skin cells shed by humans and other things found in house dust. The protein found in their droppings can trigger house dust mite allergies.

Despite its rather fierce appearance under a microscope, the house dust mite does not bite: it eats the skin flakes that make up a large percentage of house dust. The mite is so small that it is impossible to see with the naked eye.

Coping with house dust mites:

One tip that can reduce house dust mites in soft toys is to freeze them overnight. The freezing process will kill the mites. Make sure you wash the items afterwards to remove the remains of any of the mites as they too can trigger a reaction.

House dust mites thrive in moist or damp conditions so try and keep your home nice and dry - perhaps by using a dehumidifier.

Another approach is to deprive the mites of food and shelter. House dust mites live by eating house dust, so a good clean will take away a lot of their food.

Mould spores

causes-mould spore allergy

What causes mould spore allergy?

Mould spores thrive in damp conditions and can be commonly found in places like window fixtures, kitchen sinks, shower curtains and damp basements.

Many allergy sufferers are allergic to mould spores as well as pollen without realising there's a difference between the two. Although staying indoors can often mean you avoid pollen to a certain extent, it's not so simple with mould spores. Mould can grow anywhere that has the right conditions indoors, such as bathrooms. You can find moulds outside on compost heaps, in soil, rotting wood and grass cuttings

Coping with mould spore allergies

If a member of your family suffers from an allergy to mould spores, there are some simple things you can do to help them to control their symptoms and find relief. For example, try to keep damp areas such as bathrooms well-ventilated and clean using anti-mould cleaning products.

Insect bites

causes-insect bite allergies

What causes insect bite allergies?

Some people have an allergic reaction when they are bitten by insects like mosquitoes. The venom or saliva released by the insect can cause swelling, itchiness and irritation.

In the UK, insects that bite include:

  • midges
  • mosquitoes
  • fleas
  • bedbugs
  • ticks

The symptoms of insect bites can vary depending on the type of insect and the sensitivity of the person who is bitten. For example, some people may have a small, itchy lump after they are bitten, which only lasts for a few hours. Others may develop a more serious reaction, such as blistering and a number of itchy, red lumps.

Bite or sting?

As well as insects that bite, some insects sting and inject venom into the wound. In the UK, insects that sting include:

  • bees (honeybees and bumblebees)
  • wasps
  • hornets

Air pollutant and irritants



Whether your family live in a tree-lined street, a block of flats or a beautiful countryside setting, air pollution is something that we all come into contact with at some time or another.

Although some of the time we are not aware of them, high concentrations of chemicals such as nitrogen dioxide, sulphur dioxide and diesel particles pollute our air every day. These pollutants can irritate the eyes, nose and airways in all of us; but those that already suffer from allergies caused by pollens and spores may suffer more.

One of the later phases of the body's allergic response is to make the nasal passages more sensitive to irritants; this is known as "nasal hyper-responsiveness". If you or your child is particularly suffering with allergies one day or seems to become extra sensitive over a period of time, this may be the reason.

Coping with pollution

Cigarette smoke, perfume, aerosol sprays, insecticides as well as industrial pollution can all act as "irritant triggers", which can worsen the effect of symptoms of an allergic reaction. Avoid smoky rooms and, of course, if you smoke yourself, the best way to help those in your family who suffer from allergies to find relief is to give up.

Other irritants

There are other factors which should also be considered as possible causes of your allergy symptoms such as an itchy, runny nose, sneezing, watery eyes etc.

Those that have developed this extra sensitivity (nasal hyper-responsiveness) may find that things such as smoke, perfumes, strong smells or changes in temperature and humidity can trigger symptoms. It can be hard to avoid all of these things, but finding the right information on precisely what it is that affects you will make that easier.

Coping with irritants

Avoid using strong perfumes and ask close friends and family to do the same, especially at times of the year when the sufferers are most likely to be showing symptoms.

Also try to avoid sudden temperature changes; this can increase your sensitivity to allergy triggers, too.