Signs and symptoms
Bronchiolitis typically presents in children under two years old and is characterized by a constellation of respiratory symptoms that consists of fever, rhinorrhea, cough, wheeze, tachypnea and increased work of breathing such as nasal flaring or grunting that develops over one to three days. Crackles or wheeze are typical findings on listening to the chest with a stethoscope. The child may also experience apnea, or brief pauses in breathing. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze. Some signs of severe disease include:
increased work of breathing (such as use of accessory muscles of respiration, rib & sternal retraction, tracheal tug)
severe chest wall recession (Hoovers sign)
presence of nasal flaring and/or grunting
increased respiratory rate above normal
hypoxia (low oxygen levels)
cyanosis (bluish skin)
lethargy and decreased activity
poor feeding (less than half of usual fluid intake in preceding 24 hours)
history of stopping breathing

Causes
The term usually refers to acute viral bronchiolitis, a common disease in infancy. This is most commonly caused by respiratory syncytial virus (RSV, also known as human pneumovirus). Other agents that cause this illness include human metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, rhinovirus and mycoplasma. Risk factors
Children are at an increased risk for progression to severe respiratory disease if they have any of the following additional factors:
Preterm infant (gestational age less than 37 weeks)
Younger age at onset of illness (less than 3 months of age)
Congenital heart disease
Immunodeficiency
Chronic lung disease
Neurological disorders
Tobacco smoke exposure

Diagnosis
The diagnosis is typically made by clinical examination.
The Predecisional Draft document generated by the workgroup in 1998 recommended additional research in the basic epidemiology of MCS, the performance of case-comparison and challenge studies, and the development of a case definition for MCS. However, the workgroup also concluded that it was unlikely that MCS would receive extensive financial resources from federal agencies because of budgetary constraints and the allocation of funds to other, extensively overlapping syndromes with unknown cause, such as chronic fatigue syndrome, fibromyalgia, and Gulf War syndrome. The Environmental Health Policy Committee is currently inactive, and the workgroup document has not been finalized.The different understandings of MCS over the years have also resulted in different proposals for names. For example, in 1996 the International Programme on Chemical Safety proposed calling it idiopathic environmental illness, because of their belief that chemical exposure may not the sole cause, while another researcher, whose definition includes people with allergies and acute poisoning, calls it chemical sensitivity. See also
Electromagnetic hypersensitivity
Sick building syndrome
Sensory processing disorder
Sensory processing sensitivity
List of questionable diseases
Environmental health
Environmental medicine
Indoor air quality
Sense of smell#Disorders

References
External links
Multiple Chemical Sensitivity Syndrome at the Merck Manual Professional Edition