House dust mite is one of the most important causes of allergic sensitisation in the UK. The allergy is caused by proteins in the mite faeces rather than the mites themselves. These allergen proteins can trigger immune responses in the airways and skin, resulting in asthma, rhinitis (nasal) and eczema symptoms. Sensitisation to the allergen can be readily demonstrated with standard skin prick or blood tests. However, not every person who is house dust mite sensitised necessarily has symptoms. Unlike with seasonal allergens such as pollens, symptoms are not always easy to relate to allergen exposure, as the ‘house dust mite season’ is rather vague and at least some of the allergen is present all year round. One of the best indicators of the allergy is obvious and fairly immediate symptoms when stirring up dust at home, such as when clearing out old cupboards or venturing into the attic.
Probably the most important source of regular house dust mite allergen exposure is bedding. It is this regular low level exposure that mainly drives persistent symptoms. Mites live within pillows, mattresses and duvets where they find a plentiful source of food (human skin flakes) and where the environment is warm and humid. Soft toys can also harbour dust mites, so should be kept to a minimum. Likely the most important factor for the growth of house dust mites is humidity and probably one of the main reasons why house dust mites become more problematic during the winter months, with windows generally closed and the central heating switched back on. The mites particularly like humidity levels above 50%, so if you suffer from mite allergies, you might like to consider investing in a small humidity monitor (available on the internet for £10 or less). You can use this to monitor the humidity levels in your bedroom and experiment with improving ventilation to get this as low as practically possible. Definitely avoid drying clothes or towels on the radiators or on airers in your bedroom, which can also have a dramatic effect on humidity levels, as you will see if you experiment!
There is plentiful information and products available on the internet regarding other measures for reducing house dust mite levels. Sometimes the effects of these individual measures are small and research studies looking at groups of patients have often shown little or marginal benefit overall on symptoms. However, patients do occasionally tell us that they have noticed a real difference. Here are some of the measures commonly recommended:
- Microfibre bedding products are permeable to air but do not allow the passage of mites into bedding. It is preferable to buy the products from the specialist allergy bedding providers, although these are more expensive than ‘hypoallergenic’ bedding fro conventional stores.
- Washing bedding at 60ºC will kill house dust mites, although they will unfortunately tend to grow back quickly.
- Carpets can also contain plentiful house dust mites. Where possible, it is recommended to use short pile carpets but best of all is hard flooring.
- Try to avoid clutter in rooms and damp dust where possible. Use of high efficiency vacuum cleaners is also advised.
The mainstay of treatment is generally anti-allergy medications (generally anti-histamines, nasal sprays and inhalers) – these work by suppressing the immune reaction to the allergen, or the effects of this immune response.
Another approach is house dust mite desensitisation (also known as immunotherapy) which works to normalise the immune response to the allergen itself and can have more long-lasting effects. At Allergy London we regularly treat house dust allergic patients with immunotherapy that is taken under the tongue as a spray or dissolvable tablet. It is very safe and although the first dose is taken with us in the clinic, it can be taken at home thereafter. If you would like further information on this please contact our office on 0203 758 9160.