Airborne allergens and chemicals cause respiratory disease - inflammation in the nose, throat and in the lung. Lung inflammation can be expressed as asthma and/or bronchitis. Air pollution, both indoor and outdoor, plays a significant role generating airway disease in asthmatics and contributes to the overall increase in asthma morbidity.

Plant pollens cause hay fever and asthma -- the immediate form of hypersensitivity. Fungal spores in the air can trigger delayed hypersensitivity with lung inflammation that can persist and present as a chronic lung disease such as pulmonary fibrosis.

Immediate Hypersensitivity

Common allergy is the immediate or type 1 pattern that can largely be attributed to IgE and a sub-population of immune cells, the mast cells and basophils. These cells degranulate if sufficient antigen reacts with IgE antibodies which act as receptors on the cell's surface.

Hay fever is the most advertised version of type 1 allergy. Ads for antihistamines proclaim the simplest mechanism of allergy: An inhaled allergen (antigen), grass pollen, meets antibody-coated mast cells waiting in the mucosal surface of the nose. A typical hay fever attack with sneezing, itching and nose congestion results.

The droppings of dust mites are important allergens in the home that can cause asthma in sensitized people. Dust mites live in bedding, carpets, stuffed furniture, old clothing and stuffed toys. They feed on human skin shedding. Dust mites are most common in humid climates and don't survive when the humidity is below 50%. If droppings of dust mites are inhaled or come in contact with the skin, they may cause chronic rhinitis, asthma and/or eczema symptoms.

Patients who tend to have type 1 reactions are easily identified by their history; they tend to have hay fever, asthma, and eczema as do family members. This triad of allergic manifestations has been called "atopy". An inherited tendency to make excessive amounts of IgE antibody is one characteristic of some atopic individuals. Skin tests are useful in diagnosing inhalant allergies in atopic patients and will reveal some but not all food allergy. type 1 food reactions tend to be immediate, dramatic and easily recognized by patients. Typical type 1 reactions are anaphylaxis, hives, acute abdominal pain, vomiting and diarrhea.

A convenient correlation between nose-reactive IgE and skin-reactive IgE was discovered. By introducing tiny amounts of suspected antigens into the skin, a local wheal and flare reaction, similar to a mosquito bite, is produced if reactive IgE is present on skin mast cells. The association of hay fever, asthma, and skin tests with allergy practice was further confirmed by the relative success of "allergy shots". These shots came to characterize the allergist's office; other aspects of allergy practice often were neglected. Allergy shots are immunological treatments. The immune response to any reactive substance can be modified by giving repeated challenges of the reactive substances.

Delayed Hypersensitivity

A surprising number of non-smokers develop chronic lung disease without known cause. Rural agricultural workers are exposed to many air pollutants, including pesticides, herbicides and organic natural materials, which can cause disease. Their illnesses are better studied than city dwellers. At risk: 6.5 million farm workers and those who process, handle, transport, and service products traveling to the marketplace. Inhalation injury can cause inflammatory reactions (bronchitis, asthma, and/or bronchiolitis) in the airway or lung tissue reactions (alveolitis and pulmonary edema).

For example there are diseases caused by organic dusts:

1.       hypersensitivity pneumonitis (HP)

2.       organic dust toxic syndrome (ODTS)

3.       occupational asthma, and bronchitis.  

There are less defined syndromes, such as mucous membrane irritation syndrome, occupational chronic bronchitis, and non-asthmatic chronic airflow obstruction that results from exposure to high concentrations of organic dust. It is a flu-like syndrome with respiratory symptoms that develop hours after exposure. Typical exposures are working around grain elevators, saw mills and dry food processing plants. Cough, expectoration, wheezing, chest tightness and shortness of breath are typical symptoms.

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