Dear fleurP,
Content Templates modify the content when called from 'the_content' function, probably the "the_content" function is called in the description area. You need to make some adjusts if you are using Woocommerce, which is better explained here: http://wp-types.com/learn/create-an-ecommerce-wordpress-site/single-product/
Please let me know if you are satisfied with my answer and if I can help you with any other questions you might have.