All you need to know about the house dust mite
Dust Mite Studies

Why house dust mites (HDM) cause allergic disease

When people, usually with a family history of allergy, are repeatedly exposed to house dust mite (HDM) droppings they can develop a sensitivity to the digestive enzymes found in the droppings. If mite exposure continues, and their immune system consider the enzymes harmful, they risk developing house dust mite related allergic diseases of asthma, rhinitis, atopic dermatitis (eczema) and conjunctivitis.
Allergic diseases caused by house dust mites are asthma, atopic dermatitis (eczema), and chronic rhinitis. Once diagnosed, then house dust mite avoidance is essential. Here is a warning from Professor John Price, Asthma UK, "If house dust mite allergic asthmatics don't avoid the mite - their asthma can get worse".


The house dust mite

Kind permission of the London School of Hygiene and Tropical Medicine

Rhinitis is a good example of how mites can not only cause and trigger chronic allergic disease, but also reduce quality of life. Initial contact with mite droppings may have resulted in annoying symptoms of repeated sneezing or a constantly runny nose. Further exposure can lead to a permanently stuffy or 'bunged-up' nose and loss of the sense of smell.

Once chronic symptoms such as these become established, it is difficult to tell when further allergen exposure takes place because the allergic reactions are joined in one long symptom that in turn reduces the quality of life.

Chronic allergic rhinitis is a known risk factor for the development of asthma and can also lead to otitis media in children. Otitis media has been described as a malfunction of the Eustachian tube which can be induced by allergic reactions, reducing the body's ability to clear mucus. Glue ear can result.

There are three major allergens from house dust mites. They are known as Der p1, an active digestive enzyme, Der p2, not an enzyme but a protein that has the ability to mimic a bacterial invasion, and Der p23. This is a newly discovered enzyme found in the film that covers the mite's dropping

The term major allergens means that most mite allergic patients react to these allergens.


References

'Potential allergens stimulate the release of mediators of the allergic response from cells of mast cell lineage in the absence of sensitisation with antigen-specific IgE' Machado DC, Horton D, Peachell P T, Helm B A, 'Eur J. Immunol'. 1996, 26, pages 2972 to 2980

Identification of Der p23, A Peritrophin-like Protein, as a New Major Dermatophagoides pteronyssinus Allergen Associate with the Peritrophic Matrix of Mite Fecal Pellets. Weghofer M, J. Immunoloy, April 1, 2013, Vol.190, no.7, 3059-3067

Early exposure to house dust mite and cat allergens and development of childhood asthma, a cohort study', S.Lau et al, 'The Lancet', Vol. 356, pages 1392 to 1397

Differences in the antibody response to a mucosal bacterial antigen between allergic and non-allergic subjects, Hales BJ, Pearce LJ, Kusel MMH, Holt PG, Sly PD, Thomas WR, 'Thorax', 2008; 63: 221-227