Can my employer ask me not to wear jewellery for health and safety reasons?

In many cases, yes. A jewellery and loose clothing ban may be justified to prevent a potential hygiene hazard if you work in areas of food production or areas which need to be kept sterile.

Likewise, your employer can judge that loose jewellery may constitute a snagging hazard if you work with machinery. Your employer is responsible for your health and safety at work, so they are right to be cautious in these areas.

If you think restrictions are not justified by health and safety concerns talk to your workplace union rep if you have one, as they may know of any solutions to the problem which other employees have used before.