Antioxidants put simply, stop free radicals from breaking down your skin. I would say they are as important as an SPF sunblock.
The two things that will break down your skin are, the sun and free radicals. To combat the sun you use an SPF sunblock, to combat free radicals you use antioxidants.
Antioxidants will neutralise a free radical, which is a rogue molecule that comes from the environment and goes into skin and breaks down your collagen and elastin, which normally keeps your skin plump.
Antioxidants should be used in the morning as part of your protection (SPF and antioxidant) and feeding (antioxidant)of the skin, as opposed to night time which is reserved for rejuvenation or cell turnover part of your routine. Antioxidants also stimulate your collagen, help’s to keep your skin strong and be able to fight.