The use of "Lily" (unspecified species, but often referring to plants in the genus Lilium or Lilium candidum, and sometimes Hemerocallis or "Daylily") for treating sunburn is primarily rooted in traditional herbal medicine. In various folk traditions, lily extracts, oils, or poultices have been applied topically to soothe burns, including sunburn, due to their purported cooling and moisturizing properties. Traditional European herbal medicine, for example, includes references to lily oil as a skin soother used for burns, wounds, and inflammation.

However, modern scientific validation for lily's efficacy in treating sunburn is extremely limited. There are very few, if any, robust clinical studies that evaluate lily extracts for sunburn relief. Most available evidence is anecdotal or comes from historical herbal texts rather than scientific literature. Some lilies contain compounds (like mucilage) that may help moisturize or create a protective barrier on the skin, but this has not been formally studied in the context of sunburn recovery. Furthermore, lilies can be irritating or even toxic to some individuals (especially cats), so caution is warranted.

In summary, the use of lily for sunburn is supported by traditional use but lacks substantial scientific evidence. Its effectiveness is unproven, and reliance on lily as a primary treatment for sunburn is not recommended over evidence-based options like aloe vera or cool compresses.