Inhaling air brings a great variety of allergenic substances into contact
with the upper respiratory tract and the lungs. A healthy person has a
remarkable ability to filter and sort these materials and avoid disease. Immune
surveillance of the airway surfaces is constantly active and prevents most
infectious organisms from invading and causing diseases. Viruses breach this
defense even in the healthiest people and cause transient infections that
resolve usually without treatment. Influenza virus is one of the best know
invaders that can cause serious and sometimes life-threatening disease.
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, play 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.
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
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
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
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.