RUŌOD Lab

Level 10 · Safety, IFRA, Regulatory Compliance and Quality

Phototoxicity: Study Guide

Read our phototoxicity guide, then find the citrus lines in your formula, compare FCF grades and work a combined-limit problem with invented figures.

Professional 20 min study By the RUŌOD Lab team Updated

In short

Phototoxicity is a skin reaction caused by a substance plus ultraviolet light. In perfumery the classic concern is the furocoumarins in some cold-pressed citrus oils, such as bergamot. Restrictions apply to leave-on products in particular categories, and several contributing oils must be considered together. The guide explains the calculation. This study guide applies it to the citrus in your own work.

What you will learn

  • Explain phototoxicity and which materials raise it
  • Work a combination calculation
  • Choose between a grade change and a reformulation

Before this lesson: Fragrance Allergens: Study Guide

A practice problem, with invented limits

Suppose two oils carry an invented limit in your category: oil A at 0.4% and oil B at 0.8% of the finished product. Your perfume holds 0.2% A and 0.3% B. Using a sum-of-fractions check: 0.2 ÷ 0.4 + 0.3 ÷ 0.8 = 0.5 + 0.375 = 0.875, below 1. If the perfume's concentrate were raised by a quarter, the total would be about 1.09 and it would fail. Real figures, and the exact current rule, come from the Standards and guidance.

Practical exercise: Audit the citrus in one formula

About 40 minutes · You will have: a phototoxic-material audit of one formula, with its sources and dates

  1. List every citrus and other phototoxic candidate in one of your leave-on formulas.
  2. For each, check the specification, the current Standard and the grade you actually hold.
  3. Calculate each one's share in the finished product, then apply the combination rule from current guidance.
  4. Compare one cold-pressed oil with its FCF or distilled grade blind on strips.
  5. Decide whether to change a grade, reduce a line or leave it, and record why.

You have done this well if your check uses real grade documents and a dated source, and your choice mentions the odor cost. The furocoumarin issue is about UV exposure on skin, so remember the warning in your handling notes, too.

Knowledge check

1. What is a phototoxic reaction?
Show the answer

A skin reaction involving a substance on the skin plus UV light. Furocoumarins in some citrus oils are the classic concern.

2. What does FCF mean on a bergamot oil?
Show the answer

Furocoumarin-free, as stated by the supplier. It reduces this issue, but check the specification and its figures.

3. Two phototoxic oils are in one formula. Can each be checked separately?
Show the answer

No, IFRA's approach combines them. Check the current guidance on how materials are combined.

Sources

Further reading and materials

Written and reviewed by the RUŌOD Lab team. This is general education, not legal, regulatory, medical or safety advice. Example dilutions and exercises are for learning, are not validated products, and have not been safety-assessed. Completing a lesson confers no qualification. How we check these lessons.