Present in our homes and work places, dust mites undoubtedly rule our carpets. Dust mites live in 95% of homes in America and are, whether we realise it or not, of an amount that can cause amazingly severe problems. Ridding homes of these tiny arachnids will be a main priority for those families with emphysemics, asthmatics and people allergic to dust mites. Dust mites may always be present, but if their population is small, there will be fewer problems.

History

In 1920, dust was not much of a deal, but in 1921, researchers suggested that household dust might be jumpstarting asthma attacks and allergic reactions. The results of the findings did not pose a major threat to anyone, they thought, so research was ended with no regrets or afterthoughts until 1964. A man by the name of Voohorst and a group of researchers began to wonder if a mite might be the cause of allergic reactions. The team found various species of mites that were labelled collectively as house mites. The type of mite that is commonly called the 'dust mite' is scientifically known as Dermatophagoides pteronyssinus, or 'skin-eating mites'.

Taxonomy

Taxonomy is the classification of organisms by categories and descriptions. The genus, in this case Dermatophagoides, says which category an organism falls into (and may well contain many individual species) and the species describes the unique species of the organism, pteronyssinus. The genus always comes first in an organism's scientific name and is capitalised. The species, which follows the genus, is in the lower case. An organism's scientific name should always be italicised or underlined.

The Dermatophagoides pteronyssinus falls under the family Astigmata and the suborder Acaridia, or free-living mites. The dust mite and its relative Dermatophagoides farinae make up 80- 90% of all mites found in the household environment.

Biology

To survive in a human's residence, a dust mite must fight hard under threats from various dangers and conditions that aren't exactly perfect. Vacuuming is not a large threat to dust mites, but artificial heating and cooling systems can give difficulties to mites. A dust mite has no time for child's play as it rockets through its short life of 45-90 days. The dust mite can and should be considered a survivor.

Life Cycle

Which came first, the dust mite or the egg? A dust mite passes through four different metamorphic stages before reaching its adult form. The phases are egg, larva, protonymph, tritonymph and, finally, adult with either the male or the female gender.

• The Egg - After mating, the egg will develop for five to eight days before hatching.

• The Larva - When the larva emerges from its spherical prison, it will feed for three to ten days before metamorphosing.

• The Protonymph - A protonymph must wait from four to seven days before reaching its next stage.

• The Tritonymph - The tritonymph must feed on skin particles, the dead bodies of its predecessors, and other organic material in its environment and grow for around five to eight days.

• The Adult - The adult dust mite is capable of breeding within 24 hours of full development. The female can lay from 30-100 eggs at one time and a single generation lasts about 25 days.

Note, though, that because the house is a controlled environment and dust mite reproduction is not limited by seasons, all phases of dust mite development can be found at any point in the year.

Habitat

The most abundant populations of dust mites are found in bedrooms and family rooms. It is the presence of people in these rooms that allows a mite to thrive. A person might spend 75-80% of his or her time in a bedroom and so dust mites would flock there. The constant respiration of a sleeping person provides the tiny arachnids with moisture. Aquatic aquariums, humidifiers and heavily watered plants can cause the present populations to explode as well.

A human being is constantly shedding skin and other delicacies that dust mites eat, providing a food surplus and heat. In fact, dust mites love bedrooms so much that a double-bed mattress can contain two million dust mites, a six-year old pillow can hold up to a tenth of its weight in dust mite bodies and fecal matter. Another reason that dust mites prefer bedrooms and family rooms is because of the amount of upholstery, carpet, wall and window hangings that make their feeding, breeding and living grounds comfortable.

Because dust mites are 75-80% water, moisture is key to their existence. Dust mites lose the most water by laying eggs and defecating. One species of mite produces more than 20 fecal pellets daily. Dermatophagoides pteronyssinus, the mite most commonly researched, thrive in a climate of about 25°C and about 75% relative humidity (RH). A trick that dust mites have developed, to keep moist, is to cluster together, trapping moisture between their bodies. Surprisingly, these cysts or huddles, are more beneficial to males and can save half of the moisture that a solitary mite would lose. Even when moisture is plentiful or when heating and cooling systems dry out the environment, the tiny arachnids still clump together.

Scientists have discovered a valuable piece of information that may allow humans to win the war against dust mites. Dermatophagoides pteronyssinus communicate using a vast array of pheromones to locate each other. Scientists say that by interfering with these chemical communication signals, which locate a mite's peers, the mites would be unable to cluster and thus die of lack of moisture.

Diet and Digestion

A dust mite's diet consists of the basic things in your house, which are virtually impossible to get rid of. Human skin shale and pet dander¹ are among the leading foods for dust mites and also the most prevalent in a household. Skin fungi, moulds, carpet beetle, silverfish, clothes moth and roach bodies and fragments are also favourite victuals for dust mites. Most household dust includes pollen, bacteria and plant material, along with all the other things that mites eat. Dust mites consume what other creatures will not, so there is plenty to go around.

The common dust mite has a short digestive system that lends a touch of simplicity to their complicated world. The mouth, pharynx and oesophagus are the anatomical components that suck water molecules and food out of the air or off a registered target. The food travels to the ventriculus, or chamber-like stomach, and buds the food cells from the sides, grabs the food particles, breaks down the food as it travels along the gut lumen, then absorbs it as it passes through the guttural epithelium, or membrane, into the haemolymph. The digested food then needs to be excreted from the body through the anus and the rectum, at which it (the digested food) is dehydrated and packed in a peritrophic membrane. After expulsion from the body, the digestive process continues inside the pellets: they eat their own dung for up to four times.

Allergies Associated with Dust Mites

Dust mites themselves are not usually the cause of allergies in people. The protein that they produce in fecal pellets is really the main cause of allergenic reactions. Rhinitis, wheezing, coughing, itchy and runny eyes, and constant congestion of the nose and ears are some of the more common signs of an allergenic reaction. If symptoms improve outside of living quarters or worsen when linens are changed, vacuuming, or dusting occur, there may be a more serious infestation of dust mites in your house.

Removing and Preventing Dust Mite Infestations

Dust mites, like many arachnids, are hard to kill with ordinary pesticides unless directly applied to the creature. Many professionals agree that removing food sources is a more successful and much less dangerous technique to rid your home of these creatures. There are various methods and solutions that are known to either kill the mites or to neutralise the protein in the fecal matter. Some think that instead of using chemicals to temporarily solve the problem, constant prevention would be better and safer.

Many prevention methods exist that can be quickly and easily accomplished if done correctly. Polyurethane or plastic covers on mattresses, pillows and draperies are quick, semi-visible solutions that prevent the dust mites from living directly in an area that you sleep on. Removing carpets, stuffed animals and draperies are more of a dramatic solution. Washing the bed linens in hot water (over 55° C)once a week or putting sheets for a short duration in the freezer are also temporary fixes for a possibly serious problem.

Borax is a wonderful solution to end the fight against dust mites. The formula for borax is Na₂B₄O₇•10H₂O. It was originally imported under the name of 'Tincal' and is identical to the mineral kernite or rasorite except for the water content. Unlike most non-metals, borax is a good electrical conductor and gives off water when heated. Borax is a known method of controlling insects/arachnids, but is also used as a flame-retardant, and in fertilisers, sandpaper and glass. Borax works first by eating through the exoskeleton of an arachnid or insect, allowing precious moisture to escape and dehydrate the organism. Borax is also capable of suffocation.

Tannic acid, an important ingredient in the tanning of leather, is also used to prevent allergenic outbreaks caused by dust mites. C₁₄H₁₀O₉ is extracted from sumac bark or oak galls. Galls are parasitic growths that inflame a tree's tissues, causing tannic acid to be emitted. A solution of three per cent tannic acid neutralises the protein in dust mite fecal matter that causes most allergic reactions. Applying the tannic acid formula must be repeated every few months to be effective, because it only denatures the protein. Denatures means to chemically change the composition by heating or other methods.

Rosemary, one of the testing variables in this experiment, is advertised as being able to kill fleas. Fleas, like dust mites, are arachnids and are susceptible to rosemary. Rosmarinus officinalis is the scientific name of this Mediterranean plant. The oil in rosemary kills mites by drying the moisture out that mites need. Rosemary is also used in perfumes, food seasonings and liniments because of its fragrance.

Changing the conditions in the dwelling where the infestation exists can also kill the mites. Dropping the relative humidity below 50%, and raising the temperature above room temperature can also make the dust mite's environment miserable and hard to live in. Creating an intolerable atmosphere to the dust mites will kill them or make your life a little sweeter knowing that you are torturing the creatures that have tortured you.

There are several commercial products that can also kill dust mites. Acarasom, Allergen by Bissel and Dustmitex are all Food and Drug Administration (FDA) approved, and will kill dust mites and neutralise allergens. Acarasom is a product that is applied through a spray nozzle and does not seem to be harmful to humans, house pets or the environment. Dustmitex is a borate compound that is known to eliminate insects and arachnids. To apply Dustmitex, you mix the substance with water and spray on surfaces that contain dust mites. This product is clear, has no smell and will not stain light fabrics with its neutral pH and low toxicity. The last product, Allergen, is available in many forms. You can sprinkle it on carpets and furniture, and vacuum it up or spray it on draperies. Allergen is said to have low toxicity and is hypoallergenic.

As well as useful things to do to get rid of dust mites, there are also many activities that are useless. Members of a household may often dust to get rid of the excrement of Dermatophagoides pteronyssinus to prevent others from getting the sniffles, but this can lend itself to more frequent and more reactive results. The dust is stirred up and a person is more likely to inhale the disturbed dust compared to a stationary coating of dust on a counter-top or bookcase. Using a damp rag or a specially designed cloth to trap dust, or not dusting at all may limit the dust being stirred up

Another behaviour that is mostly useless is vacuuming. When a person vacuums, he or she is only pulling 5-10% of the dust mites in that area out of the carpet. The percentage of mites that can be vacuumed out of the carpet is extremely small and they can go through the fibres of a vacuum bag. A HEPA (High Efficiency Particle Arrestor) can eliminate the problem of redistribution and provides a wonderful habitat for mites.

Viewing Dust Mites

In length and appearance, dust mites are rather unremarkable. They measure about 1/25mm - 1/100mm and have a greyish, black or reddish colour. A single mite is oval in shape and has eight legs like all arachnids. The mouth and antennae parts are clumped together at the front of the body forming a sort of 'head'. Most of the time, dust mites will have tiny beads of moisture and specks of food on its exoskeleton and feet. To preserve moisture, dust mites are usually accompanied by other mites; in other words, where there is one dust mite, there are many. A microscope with at least ten-magnification power is needed to view dust mites; a dissecting microscope is suggested. Sometimes, you can even see them with a strong camera lens or magnifying glass.

Importance of Research

Dust mites are largely underestimated as a potential allergen in the house environment. In the past 20 years, research has increased on the possibility of dust mites being a serious and possibly deadly catalyst in an allergic reaction. Pollen and mould were the two most commonly assumed allergens by doctors and families everywhere, until contradictory evidence was provided. The study of Dermatophagoides pteronyssinus and Dermatophagoides farinae has risen dramatically and will most likely continue to rise due to the increase in breathing and allergy problems.