The traditional approach to the management of allergic disease is first to identify through a complete history and appropriate diagnostic testing the events or substances that precipitate the symptoms. Once this goal is accomplished, an appropriate treatment program can be organized. Traditionally, the three principal therapeutic methods have been avoidance of exposure, pharmacologie treatment to minimize or counteract symptoms, and immunologie alteration of the response to allergens. Patient education has become a fourth frequently articulated principle of management. Because allergic diseases are frequently chronic and variable, ,an informed and cooperative partnership between the physician, parent, and patient will enhance the likelihood of a good response.
Our environment can be divided into the abiotic environment with climatic factors such as wind, temperature, humidity, radiation, and other nonliving contents of the air, and the biotic environment, which includes all plant and animal materials. Numerous environmental substances precipitate or aggravate asthma by immunologie or nonimmunologic mechanisms; minimizing contact with them is the treatment referred to as "environmental control."
The Abiotic Environment
Multiple meteorologie factors create our climate. It is not always easy to assess the effect of individual factors, such as wind velocity, humidity, temperature, and barometric pressure on a child's health because it is their complex interaction that influences the quality of air and its allergen and irritant content.
Low wind velocity leads to accumulation of pollutants, whereas high velocity and turbulence disperse particulates and may decrease their concentration.
High humidity is generally detrimental to asthmatic patients. 1 This may be due to the adverse effect of altering mucosal osmolality,2 the result of increased numbers of pollen-producing plants and mites, or the greater mold growth and release found under these conditions. Some mold spores, however, are shed into dry winds, and rain decreases the atmospheric concentration of pollens and these spores.
Changes in temperature seem to be troublesome for asthmatic patients, and in particular, a sudden decrease in temperature can precipitate attacks of asthma.3 Laboratory studies have shown that all conditions that extract heat from the airway cause a fall in specific airway conductance in normal subjects and even more profoundly in asthmatic individuals.2 The onset of cold weather also requires the use of heating systems. It is likely that the increase in reactive airway problems during winter are due to a combination of cold, dry air and the allergenic stimulation of the circulated dust and mold spores in the home.4
Barometric pressure changes have long been associated with an increase in the frequency of asthma attacks. In 1933, laboratory studies documented an increase in symptoms associated with sudden barometric pressure drops,5 however other investigators have reported an increase during days of high barometric pressure.6
Considerable interest in the past has been given to the possible effect of atmospheric ions on the airway. Current data suggest that negative or positive ionization does not play a significant role in the production or aggravation of asthma. 7
Outdoor Air Pollution
Asthma, exacerbated by air pollution, is a problem of growing recognition and concern. Air pollution is defined as the atmospheric accumulation of manmade substances to a degree that becomes injurious to humans, animals, or plants. There are two main types of outdoor pollution: industrial smog and photochemical smog. The first results from the combustion of solid or liquid sulfur-containing fossil fuels, and the second from the chemical reaction of sunlight with exhaust emissions. These two types of pollution can coexist in a given area at the same time. The levels of air pollutants are affected by many weather conditions, but low wind velocity especially hinders their horizontal dispersion, and high pressure and temperature inversions limit vertical dispersion. Local geographic features that confine air pollutants also contribute to air stagnation. A significant correlation between high levels of air pollution and an increase in children hospitalized for asthma has been documented.8 Other studies have implicated sulfur dioxide,9 sulfuric acid,10 carbon dust,11 chemical irritants,12 and ozone13 in aggravating asthma. There appears to be an additive element in the combination of cigarette smoking and high levels of environmental air pollution leading to adverse effects. 1Z The Weather and Air Pollution Committee of The American Academy of Allergy and Immunology has developed the following guidelines for asthmatic patients during air pollution episodes14:
* Avoid unnecessary physical activity. Cold temperature and low humidity are additionally stressful to the asthmatic patient exercising during air pollution. l5
* Avoid smoking and smoke-filled rooms.
* Avoid exposure to dust and other irritants, such as hair spray, paint, exhaust fumes, or smoke from any fire.
* Avoid exposure to persons with respiratory infections.
* Try to stay indoors in a clean environment; air conditioning and other filters may be helpful.
* If it appears that the air pollution episodes will persist or worsen, it may be desirable to leave the polluted area temporarily.
* The physician should formulate specific instructions to be followed by the patient with regard to which medications to use, when to call the physician, and when to go to a hospital.
indoor Air Pollution
Indoor air pollution frequently involves different contaminants, sources, and atmospheric dynamics than does outdoor pollution, thus it needs to be evaluated separately. Indoor pollution is an important health fector, even in areas where the outdoor quality is good, because many children spend more than 20 hours of each day indoors. The problem of indoor pollution may be more serious now because energy conservation measures have made structures more resistant to indoor/outdoor air exchange. Mobile homes, prefabricated housing units, and energy efficient homes are especially prone to indoor air problems. Several potential indoor air quality problems are out-gassing of materials, return of air through flues and sanitation vents, and moisture build-up that leads to mold and fungus growth.16 Generally, new and better insulated structures have a 50% turnover of indoor air in 1 hour, whereas the average house has 100% turnover in 1 hour.
In about 50% of homes in the United States, natural gas or liquid propane are used for cooking. The combustion of fuels can be a source of carbon monoxide, carbon dioxide, sulfur dioxide, formaldehyde, hydrocarbons, and nitrogen oxides. Elevated concentrations of carbon monoxide and nitrogen oxide have been reported in home and schools where unvented gas heaters and kerosene heaters are used and in skating arenas with gasoline powered icecleaning equipment. Exposure to nitrogen oxide has been associated with bronchoconstriction and increased infection rates. There has been a national trend away from cleaner space-heating fuels, such as gas and electricity, and a resurgence of wood and coal burning stoves along with the kerosene heaters. The number of wood burning stoves is in excess of 1.5 million and there are over 13 million kerosene heating units in use during the winter months. Emissions from these heating appliances contain toxic and carcinogenic particles and gases. Indoor heating with wood burning stoves has been associated with increased frequency and severity of cough and wheezing compared with children whose homes are heated by other means. Eighty-four percent of children in a wood burning stove environment had at least one severe respiratory symptom as compared with only 3% in the control group. Major pollutant emission by-products of wood combustion in these stoves include carbon monoxide, nitrogen dioxide, sulfur dioxide, and respirable particulates.18
Formaldehyde exposure from building materials, such as plywood and particleboard, furnishings, and some types of foam insulation, has also been reported. Out-gassing of formaldehyde from these products can occur over a considerable period with the half-life for emissions between 2 and 5 years. Adverse effects may result from inhalation, ingestion, or contact. Formaldehyde at concentrations of 1.2 to 2.5 mg/mp 3 has been demonstrated to cause asthma in 5% of occupationally exposed persons. Whether the lower ambient levels (0.4 mg/m3) common in homes can also cause asthma remains to be determined.19
Tobacco smoke is the dominant source of particulate matter in the homes of 65% to 70% of children. Tobacco combustion contributes to concentrations of respirable particles, polycyclic hydrocarbons, carbon monoxide, nicotine, NO2, and acrolein. About 75% of the smoke from a cigarette is not inhaled by the smoker. This side stream smoke burns hotter and is considerably more toxic, especially to individuals with respiratory diseases. Homes with two or more smokers often have particle concentrations that exceed the federal standards set for outdoors.
Many substances in cigarette smoke are irritants, and conjunctival irritation, nasal discomfort, cough, sore throat, and sneezing have been noted in nonsmokers exposed to cigarette smoke.22 Other more severe changes in small airway function have also been reported in nonsmokers exposed to smoke.23 Most studies of the effect of parental smoking on respiratory health in children show an association with increased respiratory illnesses in children, especially during the first 2 years of life.24 In a prospective study of the first year of life, it was found that tracheitis and bronchitis occurred significantly more frequently in infants exposed to cigarette smoke in the home. Maternal smoking imposed greater risks upon the infant than parental smoking.25 Ibr children beyond the age of infancy when the mother smoked, the children suffered 20% to 35% excess of respiratory problems, such as wheezing, coughing, and bronchitis compared with children living in homes without smokers. Illness and symptom frequencies were linearly related to the number of cigarettes smoked by the child's mother. Illness rates were higher for children of current smokers than for children of former smokers. At present, the mechanism by which passive smoking causes decreased lung function is uncertain. It has been hypothesized that smoke damages the airway epithelium, making it more susceptible to a higher frequency and severity of respiratory infections, which in turn lead to diminished lung function. It is also possible that smokers, who are known to develop more viral respiratory infections than nonsmokers, pass these on to their children. Whether tobacco smoke sensitivity is due to an allergic mechanism or is entirely irritative has yet to be resolved. Nonetheless, tobacco smoke exerts numerous deleterious effects on host defense mechanisms, including denudation of ciliated epithelium with squamous metaplasia of the epithelium, toxic effects on ciliary function with decrease in mucociliary clearance of inhaled materials, depression of alveolar macrophage phagocytic and bactericidal activity, and increase in bronchial irritability.
The airways of asthmatic patients are known to be affected by the inhalation of a wide variety of irritants, which (in addition to those already mentioned) include insecticides, aerosols, paint, laundry detergents, cooking, and cosmetic fumes. With chronic exposure, increased susceptibility to their effect is probable, due in part to sensitization of tracheobronchial vagal receptors,26 which results in exaggerated bronchoconstrictor responses. This may be a major component in the development of airway hyperreactivity of asthma.
The Biotic Environment
There are a great number of substances in our environment that induce allergic reactions. Environmental control depends on identifying these allergens through a thorough history. Because of the total time children spend in their bedrooms, special emphasis should be directed there. Many children stay at day care centers or homes while both parents work, and these areas must also be investigated.
GENERAL MEASURES FOR CONTROLLING THE ENVIRONMENT
Environmental control measures must be based on the suspected or known sensitivities of the patient and must be developed in partnership and cooperation with the family. The first suggestions should be those that will be easiest to accomplish and least likely to necessitate a change in behavior, relationships, or priorities. Later, additional recommendations may be needed if the initial ones are not sufficient. These recommendations must take into consideration expense, lifestyle changes, and impact on the whole family. These measures require the understanding of everyone involved and a reasonable expectation that the patient will benefit.
Since allergic reactivity to various substances is a matter of degree, it may be sufficient to reduce exposure rather than totally eliminate it from the environment. Emphasis, therefore, should be placed on the known exacerbating factors and on those areas, such as the bedroom, in which a patient spends the greatest amount of time, ibr the child with more severe symptoms, more extensive measures may be needed in the entire house, in a babysitter's home, in the school room, and in the homes of friends.
With difficult problems, a visit to the home may uncover unexpected environmental factors.27 The neighborhood geography, age and nature of the house, quality of housekeeping, presence of animals or irritant odors, and compliance with previous recommendations may be directly assessed. In addition to information gathering, the effect of the home visit is to underscore the importance of instructions for controlling the environment.
House dust has been described as an allergen since 1920 and was for many years thought to be a conglomerate of plant and small animal particles. In 1967, the house dust mite, DermotopJuigoides pteronyssimus, was shown to be the major source of the house dust allergen.28 Ninety-four percent of house dust-sensitive patients give positive skin reactions to D pteronyssimus extracts and, to a lesser extent, to extracts of other species of mite. Asthma patients who are skin test negative to house dust are almost always negative to D pteronyssimus.29 The mite count is particularly abundant in mattress dust because desquamated human skin scales are concentrated here and are the main food of the mite. Patient studies have demonstrated that miteinduced asthma has a clear dose-response relationship to mite exposure and occurs more commonly in older and more humid houses.30 Repeated readings indicate the house dust mite is practically absent in rooms with an average relative humidity below 60% and that infestations reach a maximum when relative humidity is above 75%. During the winter, because heating the home results in a lower relative humidity, fewer live mites are found. In the late spring and summer, temperature and relative humidity rise, resulting in higher mite populations.31 The major mite allergens are contained in the mite feces. Each mite produces about 20 of these waste particles every day. These particles continue to cause allergic symptoms after the mite that produced them has died. Therefore, although there may be a relatively short period of optimal mite growth from June to October, mite allergen levels from the fecal remnants can remain high in mattresses and upholstered furniture through many months of low humidity. Thus, house dust mite allergy may be perennial.
Inhalation of the mite allergen is very low in early infancy with the major exposure occurring during vacuuming or bed making.32 In children, exacerbations of mite-induced asthma may occur with activities such as wrestling on the carpet or during a move from one house to another. Attacks of asthma precipitated by dust mites tend to be worse at night and early in the morning and are frequently associated with upper airway symptoms.
Measures to minimize the exposure of allergic children to house dust and dust mite have for many years been advocated as a fundamental part of therapy. 33 Reduction in bronchial reactivity and improvement in clinical symptoms and pulmonary function have been documented in adult patients living in hospital rooms34 and in children 1 month after dust control measures had been instituted in their bedrooms.35 In hospital rooms, mite allergen levels can be less than 2% of home levels. Minimizing the dust in the bedroom should be emphasized. It is a simple procedure that does not disrupt the child or the family's life and can significantly lead to improved health.
There are two classes of fungi, molds and yeasts, both of which are found in the air and can cause allergy. There is no way to separate the indoor air of any dwelling completely from the outdoor air. The types and quantity of outdoor and indoor airborne fungi in any locality are affected by the meteorological conditions, the flora and fauna of the area, and the type of neighborhood in which they are found. Ringi are most prominent throughout the growing reason in temperate areas, and peak spore levels occur in late summer and autumn, particularly during hot, breezy periods when dry spore forms are especially abundant. Spore levels are higher closer to the ground. Therefore, lawn mowing and leaf raking are activities of high exposures and should be avoided by the mold-sensitive child.
The influence of outdoor fungi is more prominent in conventionally ventilated homes than in homes where the windows and doors are airtight and cooling or heating is accomplished through central closed systems. Dark, humid, and poorly ventilated areas are optimal for indoor fungal growth. The basement, crawl spaces, washer and dryer, stored furniture, rubber carpet underpads, suitcases, bathroom walls, shower stalls, window sills, and sinks are such sites. The kitchen refrigerator contents are also a source and thousands of spores may be released into the air when the door is opened. Hingi can be abundant within cooling, heating, and humidification systems.36 The water container of portable and central humidifiers should be changed daily and chemicals have been developed to add to water sources to eliminate fungal growth. Poor water drainage, highly shaded areas, poorly maintained landscaping, large quantities of organic debris near die home, house plants, Christmas trees, fish tanks, and paper products may contribute to indoor mold growth.37
Removing or cleaning the dusty, mold-laden objects is the best remedy for reducing the numbers of indoor fungal spores. Keeping the house well ventilated is important, as is a low humidity. Air conditioning reduces humidity and filters large fungal spores, lowering the mold and yeast count indoors.38 The use of vaporizers in the bedroom rarely helps in the management of bronchitis or asthma and may only promote mold growth.
Major allergenic windborne tree, grass, and weed pollens are so prevalent outdoors throughout the lower atmosphere that avoidance measures can only curtail excessive exposure. Common sense attention to meteorologie conditions can be helpful, because low pollen counts prevail after a prolonged rain, whereas extended warm dry weather promotes dispersion. Brisk winds also promote pollen transport, which can extend over 100 miles. Awareness that morning hours are the time of peak pollen emission and that there are seasonal variations for certain pollen exposures will also aid a patient in avoiding them. Greater concentrations of pollen can be found in parks, fields, vacant lots, wooded lots, and in rural environments. Activities, hobbies, and chores, such as hiking, camping, team sports, horseback riding, dirt bike riding, and yard work, need to be evaluated in relationship to an individual's sensitivities and severity of symptoms.
Indoor pollen levels may be reduced effectively by closing windows. Air conditioning further removes pollen and mold spores from rooms, resulting in much lower counts than in rooms that are not air conditioned.39
Virtually any hair-bearing species of animal can sensitize a patient, but the degree and frequency of exposure remain critical factors in determining the level of a child's symptoms. It is the skin scale, serum, and saliva from the animals rather than the hair that is responsible for stimulating IgE production. Although some animals, notably the horse and the cat, tend to be more allergenic, none is hypo-allergenic. Sensitivity to a species of animal results in sensitivity to all varieties of that species. Some varieties may cause a varying degree of difficulty because of size, length of hair that can trap dander, and amount of skin shed. Animals, therefore, should be kept outside the allergic child's home or, if this is impossible, out of the bedroom. If the child is not yet sensitive to an animal, its continued presence promotes the development of this new sensitivity.
SPECIFIC MEASURES FOR CONTROLLING THE ENVIRONMENT
Some environments can be responsible for intractable symptoms in a child. The mechanism may be severe sensitivity to pollens and mold on a ranch or farm, air pollution from a nearby factory causing bronchial irritation, or increased airway reactivity due to a cold, damp climate. In these circumstances, a change in geographical location may be considered. Although such a move may provide short-term benefit for the patient,50 little, if any, improvement will result if indoor or food antigens are not eliminated, if new sensitivities in the new environment are acquired, or if the psychosocial and financial well-being of an entire family are compromised. Therefore, a 1- or 2month trial period should precede any permanent decision. Only in rare circumstance is such a move indicated.
* High concentrations of mite allergen may be present in upholstered furniture and carpets outside the bedroom. Minimizing the dust mite allergen level in the remainder of the house is also helpful. Vacuuming with an efficient cleaner will remove surface dust and fecal pellets, but not live mites. A central vacuum system with the motor and collection bag in the basement or garage works well. A poor vacuum cleaner with inadequate suction or a leaking bag will cause allergens to become airborne. Although basic house cleaning does not reduce the existing level of mite antigen, the failure to clean house has been shown over a 6-week period to allow a 300% increase in mite antigen level. Therefore, regular home cleaning measures are important.
* Several chemicals have been proposed for use in killing mites, but there is no commercial preparation currently available.
* Respiratory irritants, such as cigarette smoke and fumes from cleaning, cooking, and cosmetics, should be eliminated from the home environment or confined to we Il -ventilated areas.
* Patients with animal allergies react to the epidermal scales, urine, and saliva, which are readily dispersed throughout the home when dry. Severe allergy to animals may improve dramatically within weeks or months after eliminating such a highly antigenic source. Specific sensitivity should be demonstrated before this avoidance measure is undertaken. Mild sensitivities may be resolved satisfactorily by keeping the pet outside or confined to the utility room when in the house.
Patient's Bedroom (Numbers keyed to Figure)
1. Fbam rubber or waterbed mattresses are preferable for mite -sensitive patients. Kapok mattresses have twice the number of mites found in foam rubber, and innerspring mattresses have three times as many.40 Brushing and suction cleaning a mattress reduces the number of live and dead mites by over 90%. Ebr effective control, mattresses should be cleaned regularly. The mattress and box springs should be encased in zippered airtight covers and the zipper of the encasing sealed with tape to prevent leakage. If there is more than one bed in the room, all should be encased. If there are bunk beds, it is preferable to have the allergic child sleep on the top bed or to split the bunks so that the patient does not sleep under a mattress. Similarly, children should not sleep under a canopy.
2. Pillows should be encased in zippered, airtight covers, or synthetic polyester pillows that can be washed monthly and replaced yearly should be used. A patient should pack this pillow for use when traveling.
3. Bedroom clothing should be kept in a closet, with the door shut. The closet should not be used for storage of toys, equipment, luggage, or outof-season clothing.
4. Heavy curtains and fiber blinds should be avoided. Window shades or frequently laundered curtains should be used. If the child is allergic to pollen or molds, windows should remain closed as much as possible.
5. Upholstered furniture should be eliminated from the bedroom. Plain wood or plastic chairs should be used.
6. Regular washing and airing of bedding normally removes a significant proportion of house dust. The water must be hot, ie, over 158° F, to kill the mites because washing live mites out of fabric is not possible.41 Wool blankets, chenille spreads, and down comforters should be avoided.
7. Both central and portable filtering systems are available. The simplest type of filtering system is mechanical, employing closely knit fibers. The more effective filters remove particles as small as 10 µ, which is adequate for most pollens and mold spores and the major allergen associated with house dust mites. Many local heating and air conditioning, as well as allergy control companies, have mechanical filters that are more efficient than the coarse fiberglass filters found in hardware stores. Some dust particles tend to be smaller, and cigarette smoke, various aerosols, and animal danders are not adequately filtered by any mechanical filters.
Electrostatic filters charge particles in an electric field and trap them on an oppositely charged filter plate. Because they produce ozone, a strong respiratory irritant, electrostatic filters may intensify asthma in some patients. All electrostatic filters require a mechanical prefilter and an activated charcoal carbon filter to remove gaseous particles. They should be manually cleaned every 1 or 2 months.
High-efficiency particulate air filter systems (HEPAs) draw air through mechanical and activated charcoal prefilters and then distribute the air flow in a laminar fashion through the various sized glass fibers that compose the HEPA filter. This filter can also be coated with chemicals that kill bacteria or viruses borne on dust particles. These very effective filters catch all particulates greater than 0.3 µ and become more efficient with use. The HEPA filters can maintain high efficiency for 2 to 5 years. Extremely effective air filtration is possible for a distance of 2 feet directly in front of the HEPA filter,42 and this can benefit nighttime asthma if placed near the head of the bed. At flows equal to several air changes per hour, both electrostatic and HEPA filters remove particles 0.5 µ in diameter and larger with an efficiency of approximately 85%. 4i However, air filtration can only remove airborne allergens and most dust allergen only becomes airborne during cleaning and falls rapidly.44 Ninety-six percent will precipitate from the air within 5 to 15 minutes after the area is disturbed. Thus, although air filtration is theoretically helpful, it often fails to alter the patient's symptoms significantly.
8. During warm, humid summer months, cooling the house may be necessary; however, exhaust fans that pull outside pollens, fungi, and dust through the house are not acceptable, and room fans only increase the circulation of allergens. Evaporative coolers can be a source of mold growth when the water cooled is not completely enclosed in the system. The best type of cooling for the child with allergic problems is air conditioning. A central unit is reasonably efficient in filtering larger allergens and irritants. It can also prevent the high heat and humidity, which stimulate mite and fungal growth.45 Although centtal air conditioning is preferable, window units can be helpful. The windows and doors to the room should be closed and the air conditioner operated with its vent closed.
9. Electric and hot water radiant systems are cleaner sources of heat for the allergic individual than forced air gas furnace heat. On the other hand, air that does not circulate cannot be filtered, humidified, or dehumidified without the use of additional units. Vents in the child's bedroom should be closed and sealed with heavy gauge plastic to prevent dust-laden air from filling the room during furnace operation. Adequate heat can still be maintained by use of a radiant space heater or electric blanket. Dacron or electrostatic filter media are more efficient than the standard fiberglass filter and can be used as a substitute in the furnace.
10. Wall pennants, aquariums, toys, books, and house plants should be avoided. Pictures or posters that can be easily cleaned work well as decorative items.
11. Closets and drawers can be cleaned with a damp cloth, wifh or without mold retardant, and used for storing only laundered clothes.
12. If using a humidifier in the winter, overhumidification should be avoided, for normal function of human mucous membranes, a humidity level between 25% and 40% is considered optimal. Molds grow best in humidity greater than 50% and at temperatures above 37° C. Mites grow best at 75% to 80% relative humidity. Mite allergen levels will remain high with relative humidity above 50%. Keeping relative humidity below 50% is the single most important factor in reducing mold and mite numbers.46 If the relative humidity remains above 50%, air conditioning or a dehumidifier,47 or moving to a house that is structurally less humid should be considered. Sources of dampness, such as leaking pipes or defective walls or roofs, should be repaired. If the house is built on soil that drains poorly or drains toward the house, the walls may become damp through capillary action. Humidifiers and vaporizers must be cleaned regularly to control fungal growth, which can be a major source of airborne spores. (Consumers Union of the United States, 256 Washington Street, Mount Vemon, NY 10050 is an excellent source of information regarding specific heating, cooling, filtration, humidification, and dehumidification equipment.)
13. Ideally, all carpeting should be removed. Even repeated vacuum cleaning is ineffective for removing mites from carpets where they are present in abundance.48 However, in the bedrooms of most allergic children, new indoor/outdoor or lower nap commercial carpeting can be used without problems.
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