Solder flux (colophony) allergy
Occupational asthma from solder-flux fumes.
About solder flux (colophony) allergy
Solder flux made from colophony (rosin, derived from pine resin) releases fume when heated during soldering. Inhaling this fume is a recognised cause of occupational asthma and rhinitis, and can also irritate the airways. Repeated exposure can sensitise the respiratory tract so that later exposures trigger symptoms, and colophony can also act as a skin sensitiser causing contact dermatitis. Electronics assembly workers, solderers and others in manufacturing and repair who work over heated flux are the groups most commonly affected, particularly where fume is not extracted at source.
Sensitisation typically develops over repeated exposure. Once established, symptoms can appear within minutes to hours and include a runny or blocked nose, itchy eyes, cough, chest tightness and wheeze, with some workers reporting symptoms that come on later in the evening after work. A characteristic pattern is improvement on weekends and holidays and a return of symptoms back at the bench, which helps point to a workplace cause.
Diagnosis is usually coordinated through occupational health, using lung-function measurements taken at and away from work and, where relevant, patch testing for skin allergy. Management centres on controlling fume: local exhaust ventilation positioned close to the soldering point, using rosin-free or low-fume fluxes where suitable, good working practices and health surveillance. Confirmed occupational asthma is reportable under RIDDOR. Because continued exposure after sensitisation can cause lasting airway problems, early recognition and effective fume control are important.
Common triggers
- Solder flux (colophony) and products containing it
Symptoms
- Skin rash or dermatitis on exposed areas
- Sneezing, runny nose or watery eyes
- Coughing, wheezing or chest tightness
- Occupational asthma over time
Avoidance & management
- Use recommended protective equipment and ventilation
- Follow workplace exposure controls
- Wash exposed skin promptly
- Report symptoms to occupational health
- Discuss adjustments or alternatives with your employer
Sources & references
Allergy safety: what everyone should know
Mild-to-moderate reaction signs
- Itching, hives or a raised rash
- Swelling of lips, face or eyes
- Tingling mouth, sneezing, runny nose
- Stomach pain, nausea or vomiting
Anaphylaxis — call 999 (UK) or 112 (EU) immediately
- Difficult or noisy breathing, wheeze, persistent cough
- Swelling of the tongue or tightness in the throat
- Dizziness, collapse, pale and floppy (young children)
- Use an adrenaline auto-injector (e.g. EpiPen) at once if prescribed, then call an ambulance even if symptoms improve
Allergy or intolerance? A true allergy involves the immune system and can escalate quickly; an intolerance (e.g. lactose intolerance) is unpleasant but not life-threatening. The symptoms overlap, so self-diagnosis is unreliable.
Getting tested: home-testing kits based on IgG are not diagnostically valid. If you suspect an allergy, ask a GP for referral to an allergy clinic for skin-prick or specific-IgE testing and a supervised food challenge where appropriate.