What are Allergens?

Allergens are substances that trigger the immune system to promote an allergic response.

What is an allergic reaction?

People react adversely to many things, such as drugs, smoke, strong chemical smells and foods. This is often due to the body’s sensitivity to moderate or high levels of these substances. An allergic reaction occurs when the immune system reacts to a normally harmless substance by making a specific antibody to fight it. This allergy antibody is called Immunuglobulin E (IgE). Each time the person encounters the offending substance, or allergen, it will link up with lgE and attach to a special white blood cell, called a mast cell, causing it to burst and release histamine and other chemicals into the bloodstream. Histamine is the compound that causes the irritant and inflammatory reactions in allergic disease.
Allergies occur most commonly in people with a close relative having an allergy.

What are the symptoms caused by indoor allergens?
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  • Indoor allergens can affect the nose, chest skin and eyes:
  • Itchy, runny or congested nose, sneezing.
  • Irritable airways, coughing, tight chest wheezing.
  • Itching, watering, inflammation of both eyes.
  • Itchy skin, rashes.
  • Congested sinuses and headache.
  • Disturbed sleep.
  • Poor concentration.
  • Symptoms worse on waking.

Unlike hay fever, symptoms persist throughout the year although symptom severity may vary from day to day. You may improve on holiday, depending on location.

What are the causes of indoor allergies?

House dustmite droppings.

Domestic pets.

Mould spores.

House dust mites

are present in almost all houses in the UK and are the most prevalent of all allergens,
Particles in the air, causing allergic reactions in 85% of asthmatic children. The warmth and humidity in modern homes is an ideal breeding environment for them. They cannot survive in extremely dry or cold conditions, such as mountains. Like most living creatures, they require warmth, food and water and, as they cannot drink, need to absorb moisture. Therefore, our beds are a haven for these microscopic creatures, with the lg.of skin cells shed daily half pint of water sweated nightly by each of us, providing all the necessary elements for their welfare and reproduction. They also find shed skin cells to eat in carpets and upholstered furniture and also furry toys. The allergen is mainly in the mite droppings, which fragment, the fine particles becoming airborne and settling quickly into the depths of our pillows, mattresses and duvets.

Animal allergens are the next prevalent cause of allergic reactions. Cat and dog allergen is in the saliva on the animal’s shed skin cells (dander) and also on the fur. Particle size is extremely small and therefore mainly airborne and easily breathed in, causing respiratory symptoms, watery eyes and sneezing. Cat allergen, particularly, may be found on walls and ceilings many months, or even years, after the animal has left the house. It can also be found on the clothes and shoe soles of people with a cat, so is easily spread.

Smaller domestic animals, such as guinea pig and hamster, distribute allergen in the urine in the bedding. This allergen easily becomes airborne when the animal scurries around in its cage. Budgerigars and parrots are another common cause of allergic reactions to their feathers.

Mould spores are ubiquitous and present indoors for most of the year Symptoms may be latent in hot, dry weather and become troublesome on damp days. Mould spores are present in houses that have obvious damp patches on walls, black mould on window frames, in bathrooms and kitchens, particularly round refrigerator door seals and shower curtains. The water reservoirs of dehumidifiers can be a breeding ground for moulds if not emptied, cleaned and dried daily. Spores are sometimes hidden underneath wallpaper and commonly present in the soil of house-plants. Houses built in areas of underlying water are often damp.

Identifying The Causal Allergen

This is what all sufferers most want to do but are rarely offered allergen diagnosis or even advice. Identifying the causal allergen is the first step in taking control of your allergy with a subsequent reduction in symptoms and medication.

You should be referred to an Allergy Specialist for diagnosis. Your levels of specific gE will be measured by either skin prick or CAP or RAST brood testing. This, together with history, symptoms and examination will enable the allergist to correctly diagnose your condition and plan your future management. Some GPs, with a special interest in allergy, may perform skin prick testing. This is a painless procedure in which one drop of each allergen is placed on the skin (usually on the lower inner arm), pricked with a specially designed lancet and blotted. If you are allergic to that substance, a small wheal of approximately 2-6mm, surrounded by an inflamed area, will appear within 15-20 minutes. This will itch for a short time before fading.

Controlling Indoor Allergens
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  • Reducing house dust mite levels
  • Increase ventilation: Open windows and doors; do not block up open chimneys.
  • Reduce the heat turn down the central heating, especially in bedrooms.
  • Damp dust.
  • Reduce humidity: keep kitchen and bathroom doors closed when cooking or running hot water Do not dry wet washing indoors
  • Enclose mattress, pillows and duvet in allergen barrier covers. (Mattress covers should be totally enclosing, not like a fitted sheet.)
  • Wash all bed linen at 600C weekly.
  • Wipe the barrier covers over with a damp cloth when you change the bed linen and allow to dry thoroughly.
  • Vacuum frequently, Preferably in the morning, with an approved vacuum with a HEPA fitter
  • Put furry toys in a plastic bag in the freezer for 12 hours, at least monthly. Let thaw slowly.
  • Replace carpets with hard floors, e.g. wood, vinyl, sea led cork.
  • Replace heavy curtains with roller or vertical blinds, or lightweight washable curtains.
  • Reduce unnecessary soft furnishings.__

Reducing animal allergens
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  • Do not buy a new animal.
  • Animals should not be allowed in the living area and never in the bedroom.
  • Wash cats and dogs weekly.
  • Groom dogs regularly outside.
  • Wash all bedding and soft furnishings on which an animal has lain.
  • Wash everything, including walls, if you have a cat.
  • Enclose bedding in allergy covers, as for house dust mite avoidance, if your animal has slept on your bed.

Reducing moulds
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  • Increase ventilation
  • Open windows and close doors of kitchen and bathrooms when
  • running hot water or cooking.
  • Keep wardrobe doors ajar and do not pack clothes in tightly.
  • Clean all mould on refrigerators, windows, walls with bleach or approved solution, rinse and dry thoroughly.
  • Do not hang wet washing indoors.
  • Reduce house-plants. Change soil regularly if you must have a plant.


[boxibt style=”success”]Information Courtesy of

The British Allergy Foundation,
Deepdene House, Bellegrove Road, Welling,
Kent. DAI6 SPY.

(Registered Charity Number 1003726)
Office Telephone Number: 0208 303 8525
BAF Helpline Number: 0208 303 8583

For Further information visit the website: