Health surveillance is a personal health assessment required under various health and safety Regulation (including COSHH), particularly where you are exposed to hazardous substances, including those causing asthma and dermatitis.
The health check may be as simple as a regular visual examination of your skin to check for signs of dermatitis, such as redness, cracks and blisters. Or it may involve a urine test or blood test, for example, if you work with lead or two-pack paint spays containing isocyanates.