Asthmatic here. The preventer inhaler, usually brown, contains a corticosteroid which helps keep the airways long term and minimises the risk of reacting to triggers. The reliever inhaler, usually blue, opens the airways in the short term, and is used when symptoms worsen in response to a trigger. It's also the one you'd reach for to treat an asthma attack with up to 10 puffs. You can also get combined preventer and reliever inhalers, and tablets like Montelukast for people with harder to treat asthma (like me).
Inhaled steroids don't cause the same issues as tablet steroids like prednisolone - I took the latter last year as my asthma was bad following a chest infection and promptly caught my husband's cold that I had successfully avoided until that point!
The most important thing is for asthmatics to keep using their preventer inhaler as prescribed, even when they feel well and to ensure they always have their reliever inhaler on them. You can check inhaler technique online, or ask your GP's asthma nurse, or a pharmacist to check it as well to ensure you're getting all your medicine into your lungs.
OP - I would check your relative has plenty of inhalers (sometimes young people ration them to avoid prescription charges and get ill, or worse, as a result). Make sure they are taking them as prescribed and know how to follow their asthma action plan, and that those around them know what to do in an asthma attack.