What should a barber do upon noticing an allergic reaction in a client?

Upon noticing an allergic reaction in a client, the appropriate and professional response is to stop the service and seek medical assistance if needed. This is crucial as allergic reactions can range from mild to severe and potentially life-threatening. It is the responsibility of the barber to ensure the client's well-being and safety, which means recognizing when a situation exceeds the realm of the barbering profession and requires medical intervention.

Stopping the service immediately allows the barber to assess the situation without causing further distress or harm to the client. Seeking medical assistance, particularly in cases of severe reactions like anaphylaxis, is essential and can be lifesaving. This response indicates responsibility, care for the client's health, and adherence to professional standards within the barbering industry.

The other options pose various risks. Continuing with the service disregards the client’s health and could exacerbate the allergic reaction. Informing other clients may not be appropriate as it could cause unnecessary concern or panic, and it diverts attention from attending to the affected client. Applying ice might provide temporary relief but is not a substitute for proper medical evaluation and care, as it does not address the underlying allergic reaction. Thus, stopping the service and seeking medical assistance is the most responsible action a barber can take in this scenario.