Reactive Airways Dysfunction Syndrome (RADS)

How RADS develops

A high concentration of an irritant damages the lining of the airways. The injured airways become inflamed and hyperreactive, narrowing easily in response to everyday triggers such as cold air, exercise, perfumes and smoke. Unlike allergic asthma, RADS does not involve sensitization to a specific substance; the airway injury itself causes the problem.

RADS is the best-defined form of irritant-induced asthma, which is one type of occupational asthma when it happens at work. It behaves much like ordinary asthma once established. A related, more debated condition can follow repeated lower-level exposures.

Common causes

Diagnostic criteria

The classic criteria include:

1. no history of asthma or chronic respiratory disease before the exposure
2. a single, specific exposure to a high level of irritant gas, vapor, fume or smoke
3. onset of asthma-like symptoms within 24 hours, persisting for at least 3 months
4. symptoms that resemble asthma: cough, wheeze, breathlessness
5. evidence of airway obstruction or hyperreactivity on lung testing
6. other lung diseases ruled out

Symptoms

• persistent cough, often dry
• wheezing
• chest tightness
• shortness of breath, especially with exertion
• symptoms triggered by cold air, exercise, strong smells, smoke or cleaning products
• night-time symptoms

Diagnosis

• Detailed exposure history: what, where, how long, how intense, and any symptoms before the exposure
• Spirometry: may show airflow obstruction that improves with a bronchodilator
• Methacholine challenge test: shows airway hyperresponsiveness when spirometry is normal
• Chest X-ray or CT to rule out other lung injury, such as chemical pneumonitis
• Peak flow monitoring at home and work
• Review of earlier medical records to confirm no prior asthma

Treatment

• Immediate care after exposure: fresh air, oxygen, bronchodilators, and observation for lung injury
• Inhaled corticosteroids to reduce airway inflammation, often for months
• Bronchodilators: albuterol for symptoms, and long-acting bronchodilators with inhaled steroids if needed
• Short courses of oral steroids for severe early symptoms
• Avoid irritants: smoke, strong cleaning products, perfumes, and further exposure at work
• Workplace changes: improved ventilation, protective equipment, or reassignment
• Treat related conditions such as rhinitis and acid reflux
• Vaccinations against flu and pneumonia

Outlook

Many people improve gradually over months to a few years, but a substantial number have long-term symptoms and airway hyperreactivity. Earlier treatment and avoiding further exposures may improve outcomes.

Workplace and legal aspects

RADS often follows workplace accidents. Documenting the exposure, symptoms and medical assessments is important for workers' compensation. Employers must report serious exposures and implement controls under occupational safety rules.

Prevention

• never mix cleaning products, especially bleach with ammonia or acids
• store and handle chemicals according to safety data sheets
• use ventilation and respiratory protection at work
• train workers in spill response
• evacuate and seek care after significant exposures

Frequently asked questions

What is reactive airways dysfunction syndrome?

RADS is an asthma-like condition that develops within 24 hours after a single high-level exposure to irritant fumes, gases or smoke in someone without previous asthma. It causes cough, wheezing and breathlessness that last for months or longer.

Is RADS the same as asthma?

RADS is a form of asthma caused by irritant injury rather than allergy. Symptoms and treatment are similar to asthma. The difference is how it starts: suddenly after one intense exposure, in someone who had healthy lungs before.

How long does RADS last?

By definition, symptoms last at least 3 months. Many people improve over months to a few years with treatment, but some have persistent asthma symptoms long term. Avoiding further irritant exposure helps recovery.

What chemicals cause RADS?

Common causes include chlorine gas, ammonia, acid fumes, sulfur dioxide, smoke from fires and spills of industrial chemicals. Mixing household bleach with ammonia or acidic cleaners can also release enough gas to cause it.