Patch testing for eye cosmetics should be used to detect allergies to dyes and preservatives near the eyes. What is the recommended observation period before proceeding?

• A. Observe 24-48 hours.
• B. Observe 1-2 hours.
• C. Observe 72 hours.
• D. No observation time is needed.

Answer: (C)

Observation over about 72 hours is needed because allergic reactions to eye cosmetics, like dyes and preservatives, are a delayed-type response that may not appear immediately. While some irritation can show up within a few hours, many true allergic reactions develop over 2–3 days, so giving a full 72-hour window helps ensure you don’t miss a late reaction before applying products near the eyes. Shorter observation times (24–48 hours or just a few hours) can miss these late-onset responses, and skipping observation altogether is unsafe because a reaction could still be developing.