Read & Send Messages
This should be fairly obvious - Wellness needs to be able to read commands and send them back at users..
Wellness primarily uses embeds to deliver images in messages. Without this ability, image commands won't work properly.
Some Wellness commands require the bot to attach image and audio files to the message. Without this ability, certain commands won't work properly.
Wellness has a setting for users, where it will delete the command message to clean the channel. In order to do this, the Manage Messages permission must be enabled on the server. However, this functionality is not required.