If you want to, it's possible to exclude browsed or purchased products from your Recommendation SmartBlocks using Filters:
Go to Content > SmartBlocks.
On the Recommendation tab, select your SmartBlock, then select EDIT.
Select the Filtering tab.
Drag and drop the Exclude Recent Activity filter into the filter list:
Adjust the filter configuration according to your requirements.
You can apply the Exclude Recent Activity filter more than once to further exclude recommendations according to your criteria.Select SAVE.