Celery "contains photosensitive substances". Celery produces a class of substances called "furan coumarin" in order to resist the invasion of pests and diseases, among which the more famous one is called "psoralen". It is a small molecular substance, which can directly act on the skin or be taken orally. Psoralen can significantly increase the sensitivity of skin to ultraviolet rays, thus making the skin easy to get sunburned and tanned.

Some people think that the daily consumption of celery will not reach this level, but some experts warn that after using this light-sensitive vegetable in summer, it should not be exposed directly.