Restricted and Prohibited Materials and Their Limits
Reading a restriction correctly
The core skill in this domain is translating a Standard into a usable maximum concentration. Restrictions may be expressed as a percentage of the finished product, as a percentage of the fragrance compound, or as an absolute mass limit. Some are expressed as the amount of a specific constituent - for example a natural oil may be limited because it contains a restricted allergen or a phototoxic furanocoumarin. The trap is applying the limit to the wrong matrix.
Prohibited versus restricted
Prohibited materials cannot be used at all as fragrance ingredients. Restricted materials may be used up to a limit, sometimes with additional conditions such as a purity requirement, a requirement that a stabiliser be present, or a restriction only for certain product types. Candidates should know that a material can be prohibited as an added ingredient while being tolerated as an unavoidable trace contaminant below a specified level.
Phototoxicity and sensitisation limits
Some restrictions exist because of phototoxicity (typically relevant to leave-on products exposed to sunlight, such as sun products and body lotions) and others because of skin sensitisation. A frequent trap: a limit that applies only to products exposed to the sun, not to rinse-off products. Another: limits that differ between fine fragrance, leave-on cosmetics, and household products.
Worked example
A Standard limits a material to 0.02% in leave-on products and 0.2% in rinse-off products. A body lotion uses a compound at 4%; the compound contains 0.3% of the material. The material in the finished product is 0.04 × 0.003 = 0.0012% = 0.0012%, i.e. 0.0012% - well under 0.02%. Had the same compound gone into a shower gel, the rinse-off limit of 0.2% would also be met. The lesson: compute the finished-product concentration, then compare against the category-specific limit.
Documentation traps
Questions may ask what evidence supports a restriction - read-across, quantitative risk assessment, or historical data. Know that limits are periodically revised as new data emerge, and that a compliant formula today may need reformulation after an amendment.