You can take Seretide and Ventolin alongside each other, because they’re different types of inhalers. Seretide is an inhaler that helps to prevent asthma, and you’ll use it as a regular medicine you take every day at set times. Ventolin is an on-demand inhaler that helps to relieve asthma symptoms when you get them. So they do different jobs.
On occasion, you might be advised to use your reliever inhaler immediately before your preventer inhaler, because this can sometimes help you administer the preventer dose better.