Somewhat rare “prurigo pigmentosa” and probably depends on how much stored toxins you naturally carry in your fat cells. I only got it a month after being keto and never again. Another thing to note with ketogenic and carnivorous diets is that it takes maybe 2-3 years for linoleic acid (seed oils) to be metabolized from adipose fat. Depends on body composition and probably varies person to person. I really noticed a big difference in how slowly I sunburn after two full years of pretty restricted carnivore (beef and water). Some say this may be inflammatory seed oils in skin and proper O3-O6 balance in the body but to me it’s anecdotal.