Aerosol inhalers containing CFCs are to be phased out and replaced with more environmentally friendly alternatives.
The change will affect people with asthma who use beige, brown or dark red preventer inhalers that contain CFCs. But those who use blue reliever inhalers will not be affected as these are already CFC-free.
CFCs have a long history of use in asthma inhalers but are now being gradually phased out due to their damaging effect on the earth's ozone layer.
Kate Jarvis, health and promotion manager for Asthma UK, said: "If you use a CFC-containing preventer inhaler, you should continue to use it as prescribed unitl you have had a consultation with your doctor or asthma nurse and together you've agreed an alternative."
Asthma nurses are charged with telling patients how to use and take car of their new inhalers. They should also provide patients with updated written personal action plans to help them manage their asthma, says charity Asthma UK.
Asthma UK has produced a fact file that lists all the affected preventer inhalers and their CFC-free alternatives.
It also provides more general advice about the switch to CFC-free inhalers, these can be downloaded from asthma.org.uk/cfcfree