Expanding polyurethane foam contains isocyanates while uncured. It is a respiratory sensitiser and skin irritant, and needs ventilation and skin protection - especially with larger spray-applied jobs.
Controls should be applied in order — eliminate or substitute first, then engineering controls, then PPE as the last line.
Yes - uncured foam contains isocyanates, which are the leading cause of occupational asthma. For occasional gap-filling the risk is lower with ventilation and gloves, but larger spray-foam work needs the same care as isocyanate spraying.
Do not use solvents, which drive it in. Use a proprietary foam remover on skin while still wet, or let it wear off, and wash with soap and water. Better still, prevent contact with gloves.
Complys writes a expanding foam (pu foam) COSHH assessment tailored to how you actually use it, in minutes — COSHH 2002 compliant, editable, with review-date tracking. Your first is free.