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Reactive airways dysfunction syndrome and irritant-induced asthma

Catherine Lemière, MD
Louis-Philippe Boulet, MD
André Cartier, MD
Section Editor
Peter J Barnes, DM, DSc, FRCP, FRS
Deputy Editor
Helen Hollingsworth, MD


Reactive airways dysfunction syndrome (RADS) and irritant-induced asthma (IIA) are closely related forms of asthma that result from a single exposure to a high concentration of irritant agents or repeated exposure to moderate to low doses of irritant agents [1-3]. Irritant-induced respiratory problems were initially described among industrial workers and World War I combatants in the early part of the 20th century [4,5]. These reports focused on acute effects such as pulmonary edema and death, but also described chronic respiratory sequelae of intense, brief exposure to inhaled irritants [5].

Subsequently, bronchitic symptoms, such as cough and wheezing, were described following a chlorine spill in 1969, although bronchial responsiveness was not assessed [6]. Persistent airway hyperresponsiveness was noted in five of seven subjects four years after an acute exposure to sulfur dioxide [7]. Further studies have led to a growing awareness and understanding of RADS and IIA, especially in firefighters, rescue personnel, and people living in the vicinity of the World Trade Center site in September 2001 [1,8,9].

The diagnosis and management of RADS and IIA will be reviewed here. The diagnosis of asthma and the causes, evaluation, and management of occupational asthma are discussed separately. (See "Diagnosis of asthma in adolescents and adults" and "Occupational asthma: Definitions, epidemiology, causes, and risk factors" and "Occupational asthma: Clinical features and diagnosis" and "Occupational asthma: Management, prognosis, and prevention".)


Reactive airways dysfunction syndrome (RADS) is described as the development of respiratory symptoms in the minutes or hours after a single accidental inhalation of a high concentration of irritant gas, aerosol, vapor, or smoke; these initial symptoms are followed by asthma-like symptoms and airway hyperresponsiveness that persist for a prolonged period (table 1) [1]. RADS can occur after exposure to a variety of chemicals generated as gas or aerosol, or exposure to high levels of particulates (table 2). Clinical and functional criteria for the diagnosis of RADS are listed in the table (table 1) [1].

Irritant-induced asthma (IIA) is a more general term to describe an asthmatic syndrome that results from a single or multiple high dose exposure to irritant products [10]. When only a single, high-dose exposure has been responsible, the term RADS or "acute onset IIA" is used [3]. IIA caused by multiple exposures to high doses of irritants which induce acute symptoms requiring acute medical care has also been reported [11]. The term "sub-acute IIA" has been proposed to describe instances of multiple high exposures to irritants where the onset of symptoms may be more insidious, as seen following the World Trade Center catastrophe [8,9], or less well-documented exposures in which the affected individuals are able to identify the timing, nature, and frequency of events [10,12]. When IIA is caused by workplace exposures, it is considered a type of occupational asthma, the non-immunologic type.

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Literature review current through: Oct 2017. | This topic last updated: Nov 02, 2017.
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