WordPress WYSWYG Editor removes Rel Tag

Hi,

This is my first post on wordpress forum, i have integrated a plugin into my wordpress website that displays tooltip on an image.

that plugin requires two attributes to display tooltip on specific image

1) title=”description”
2) rel=”tooltip”

and it works fine, when i make changes to same page where i implemented above two attributes on image tag, wordpress editor removes REL tag.

any one guide me what could be the issue and how i can prevent?
i am not using any SEO plugin so far.

any help would be appreciated.