What is Reactive Airways Dysfunction Syndrome?

Did you know that asthma subtypes can have subtypes themselves? Well, I don’t know if my assessment there is totally accurate (I’ll have to direct that to Asthma.net subtype expert John!), but that’s how it seemed to me when I learned about what’s called Reactive Airways Dysfunction Syndrome (or RADS).

A couple of months ago, an asthma researcher I do some work with started the process of looking into research grants to study RADS. Like one does, I started Googling to get at least some degree of smartness about this topic seeing as apparently I am maybe about to co-author a paper on this (also like one does, I just Googled for statistics about how often I use Google…). As it would turn out, the difference between “general” occupational asthma (OA) and RADS is quite interesting.

Two types of occupational asthma.
There are two different types of occupational asthma (as I’m sure you’ve gathered by now)—the difference is typically both in how a person responds to the trigger and what type of substance triggers the reaction.

Allergic occupational asthma vs. RADs

In what is probably the better-known type of occupational asthma (if there is a better-known type!), a person who has had many exposures to a workplace allergen begins experiencing asthma symptoms.1 The many exposures where no symptoms occur is what is called a “latency period.”1 It might compare to how we must become ‘sensitized’ to an allergen—for instance, reactions at first may be so mild that they are not noticeable, or no reaction at all exists. The allergic reaction may continue to worsen with additional exposures—in this case, the onset of asthma symptoms in response to the trigger. This type of occupational asthma is more likely to occur in people with a pre-existing diagnosis of asthma. This is known as immunologic occupational asthma, as it is based on an immune system reaction (IgE response) to an allergen.2

Reactive airways dysfunction syndrome

Converse to the immunologic reaction in the first form of OA, the reaction type in RADS is non-immunologic (or, non-allergic), and is found in people with no previous reported or documented respiratory disease, such as pre-existing asthma.3 This reaction most often occurs in response to an irritant type trigger, rather than an allergen.3 RADS is usually caused by a high concentration, single exposure to a chemical irritant, but sometimes may be caused by multiple exposures to chemicals.4 After the onset of RADS, it is indistinguishable from other types of asthma4, but the origin can be traced to a single event exposure. Symptoms of RADS typically onset within 24 hours of the exposure to a large amount of inhaled chemical, smoke, gases, or vapors with “irritant properties”3, but symptom onset can occur almost instantly, within minutes, and symptoms may be very severe or even life-threatening.5

Treating RADS

As a type of occupational asthma, treatment of RADS is no different from treating other forms of asthma—using bronchodilator and inhaled corticosteroid medications to both prevent and relieve symptoms.5 As with all forms of asthma, it is important to stay away from being exposed to the trigger or triggers of the RADS episode.5 Workplace chemicals may be swapped for a less irritating kind, or a worker may need to wear a particle filtering respirator while working to prevent further exposure to chemicals at work.5

Before RADS was mentioned to me in this phone call a few months ago, I had never heard of this form of occupational asthma—yet despite a fair amount of information being available online, I couldn’t determine how many people RADS specifically affects—so indeed, more research needs to be done!

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