Updated 07 May 2018

Facts about dust mites

The house-dust mite (Dermatophagoides pteronyssinus) is a small eight-legged creature. You cannot see it with the naked eye. It is about 0,33 mm long.

The house-dust mite lives in places where it is warm and humid such as human bedding, carpeting and upholstery. There are about 10 000 house-dust mites in the average bed, according to the Allergy Society of South Africa.

It feeds on the dead skin scales of humans that have been modified by a fungus.

The female mite lays about 50 eggs in her six week lifespan.

Some people are allergic to the protein Der.p.1 in the excretion pellets of the mite. About 20 pellets are excreted by each of the 10 000 mites in your bed every day. The allergic reaction follows after a person breathes them in the air.

House-dust mite allergies can be identified by skin prick tests (SPT) or RAST tests on a blood sample.

Read more:
Visit the Healthy Home Centre
Allergy Society of South Africa (ALLSA)
National Asthma Education Programme (NAEP)


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Dr Morris is the Principal Allergist at the Cape Town and Johannesburg Allergy Clinics with postgraduate diplomas in Allergology, Dermatology, Paediatrics and Family Medicine dealing with both adult and childhood allergies.

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