Mite Allergens and the Allergic March
8/1/2003
By Acarologist Frans Kniest
Despite the daily cleaning of the home, a layer of dust will still cover the floor and furniture. Dust is defined as a collection of particles that can be airborne. When a beam of sunlight falls at a low angle in a darkened room, you can see the dust floating in the air. House-dust is continuously produced in the human habitat. People are the dominant creator of house dust. Daily activities and cleaning of the home cause friction with the different materials that produce dust. Dust originates not only from furniture, furnishings and clothing, but also from the inhabitant itself (dander, hairs, etc.). In addition to humans, other living inhabitants such as mites live in the dwelling and produce their own form of dust (bodies and droppings). These particles become part of the house-dust.
The allergy causing mites, most commonly found in dwellings worldwide, are called house dust mites. Although we know over 100 species that can be found in house dust, 4 mite species occur most often in homes in the United States. Predominant species are Dermatophagoides farinae and D. pteronyssinus (the European and American house-dust mite). Most homes in the United States are co-inhabited by these two species, although some homes only contain 1 species. These mites are the source of multiple potent allergens in house dust, including the mite itself and in higher quantities the droppings of the mite. It is a good idea to know what mite-allergens really are and what they can do.
For many people (the non-atopics), these mite bodies and their droppings do not cause any problems. After entering the body (inhaling or eating) they do not cause any disease, they are not poisonous and they do not smell; they are harmless. In fact, these normal dust components are treated as harmless foreign proteins/enzymes by our bodies.
For another group of people (the atopics), these “harmless” substances cause more harm than good. Bodies of atopics identify these substances as harmful foreign proteins that have to be destroyed (like bacteria, viruses and parasites), and the reaction switches from “in rest” to “attack”. Attack means to fight a battle against the invaders. Unfortunately no invaders are present and to attack these harmless substances does not help. Symptoms tend to increase over time, getting more excessive and worse as a person gets older. Conjunctivitis, rhinitis, eczema and asthma are the typical outcomes of this fight.
Beginning in the year 1906, substances that caused this “not normal (allergic) reaction” were called allergens. At that time this allergic reaction was considered to be an immunological phenomenon. In the case of inhalant allergens, the immunological reaction partners were called allergen and reagin. The allergens were the foreign proteins/enzymes from the house-dust. The reagin was disclosed later (in 1967) and was called Immunoglobulin E (IgE). This IgE is the body’s own component of our immune system.
The Allergic March
The term “allergic march”, especially in children and adolescents, refers to a characteristic sequence in manifestation and remission of atopic symptoms. In many cases the atopic march starts in the first weeks of life. This is mainly directed against food proteins, especially those found in hen-eggs and cow-milk.
Clinically seen as the first step of the atopic march is atopic dermatitis (eczema). This is then followed by rhinitis, and ending with asthma. Without adequate treatment, allergic diseases march into more and more dramatic complaints, and can eventually result in death from asthma. Therefore it is important to stop this allergic march as soon as possible. Avoidance of the allergens and its producer, as well as an adequate therapy (allergen shots and medication) is the way to go to reduce the affects of allergens.