In the UK, there are regulations to be followed with regard to wax melt sales under the EU’s Classification, Labelling & Packaging Regulation (CLP for short) which after 1st June 2015, stipulated that all new products with hazardous substances must be labelled accordingly. CLP applies to a non-cosmetic product of any size containing a hazardous substance such as fragrance or essential oils.
If the product is not classified (i.e. it DOESN’T contain any ingredients that are classified as hazardous) then there is no requirement for it to be labelled in accordance with CLP. The wax used in candles, is very unlikely to be classified as hazardous and instead it is the fragrance oils that will be the main concern.
Many ingredients in the fragrance oils are known to be eye or skin irritants and environmentally hazardous substances. If present at certain concentrations, they trigger various health or environmental warning statements and safety pictograms. Each product should have a unique CPL label, one label will not suffice for two different scents as an example.
NEVER purchase a non-cosmetic fragranced product without labelling: it is not EU compliant and quite simply is illegal to sell in the UK. (Do be aware, other countries are not necessarily required to be CPL compliant!)