Sew Fine Thread Gloss is a beeswax-based scented (and unscented) thread conditioner to help make your hand-sewing less tangly, smelling fantastic, and an all-together more enjoyable experience
The fragrance oils used are phthalate-free and safe to use in cosmetics products. This is important because, although Sew Fine Thread Gloss is not a skin/body product, it does come into contact with the skin of your fingers, and even the slightest amount of absorption of any kind needs to be considered. Aimed for a light ratio of fragrance oil, so that the scent is not overpowering there is also a "natural" thread gloss which is essentially, unscented with fragrance oils and is only the natural scent of the beeswax.
Also to note, Sew Fine does NOT use essential oils. Why? Essential oils are natural oils extracted from the plant it is derived from. Being a biological product makes it prone to aging and decomposition, regardless of any chemicals used to prolong its life. Aka - they have a shelf life. As they age their fragrance can change (they go rancid) and the oil itself darkens. For a product that may leave traces on your treasured quilts, and would hate for these oils to weaken the threads and potentially weaken and stain the fabrics. Sew Fines' Creator is a quilter too, and I would never use essential oils in their product for those reasons.