... high-dose vitamin D provides relief from sunburn ?

This is exactly what a study (source at the bottom of the email) examined in 2017.

Subjects should take a high dose of vitamin D within the first hour after a sunburn. Then the vitamin reduces significantly:

• Skin redness
• swelling
• Inflammation

The 20 participants in the study received either a placebo preparation or 50,000, 100,000 or 200,000 IU of vitamin D one hour after they got a sunburn. The test subjects and their sunburn were then examined 24, 48 and 72 hours and 1 week after Vitamin D intake. Skin samples were also taken so that further tests could be carried out.

Conclusion of the study: The higher the vitamin D level was in the participants, the less reddening the skin was . At the same time, an enormous increase in the activity of those genes that were responsible for the main repair was seen in these test subjects.

Sources:

• Jeffrey F. Scott, Lopa M. Das, Sayeeda Ahsanuddin, Yuqi Qiu, Amy M. Binko, Zachary P. Traylor, Sara M. Debanne, Kevin D. Cooper, Rebecca Boxer, Kurt Q. Lu.Oral vitamin D rapidly attenuates inflammation from sunburn: an interventional study. Journal of Investigative Dermatology , 2017, (Oral vitamin D intake rapidly reduces inflammation from sunburn: an intervention study)
• Case Western Reserve University. "Vitamin D may improve sunburn, according to new clinical trial: Results show high doses of vitamin D reduce swelling, inflammation." ScienceDaily, July 6, 2017, (Vitamin D may improve sunburn, new clinical study finds: Results show high doses of vitamin D reduce swelling and inflammation)