Wanna share my experience, the TL;DR is that if you feel well you shouldn't expose yourself to the sun or use parasol or sunscreen, because only narrow UV spectrum is good, and sun doesn't care.
I've had a severe form of psoriasis, majorly on scalp. Over 1/3 scalp looked like it had been rubbed with a sandpaper to near-bleeding sores. I tried to different docs, nobody told me what it is, I had no option but to do my own research.
I found that it can be treated with ultraviolet, but not all of UVs are good for you, there are UVA, UVB and their sub-spectrums. The only good for health UV is UVB with a narrow peak at 310nm wavelength. Those tanning beds for bronze effect are wide band UVA+UVB and not good at all neither for vitamin D, nor for your health in general.
So I had bought a UVB 310nm medical lamp, shaved my head, and started using UVB since june, it's been a half year experiment on myself. I started with long, over 10 minute sessions to figure out a limit where I do get burned (>10 minutes). Later I reduced down to 5 min, two times a week, and almost haven't used UVB recently. I don't have vitamin D blood meter, my criteria is a state of my skin, i.e. absence of pain on palpation, less itching, no bleeding sores, no reddening. Looks like UVB works for me, what I can tell from my experiment.
In comparison with sun, UVB lamp with timer showed to be more safe, IMO. Three hours outdoors w/o sunscreen gives a sunburn very likely; but a 5 min/day UVB lamp exposure seems to be safe.
I have a few tiny colored skin patches over body, didn't cover them or anything, just ignored them; they have become less distinguishable after UV. However, if you have patches like birthmarks, you must track their borders. When borders become blurred, that's a not good sign, you gotta them checked by your dermatologist. I think there could be some app to track colored skin patches, there is a bunch of open source libs for that[1].
I've had a severe form of psoriasis, majorly on scalp. Over 1/3 scalp looked like it had been rubbed with a sandpaper to near-bleeding sores. I tried to different docs, nobody told me what it is, I had no option but to do my own research.
I found that it can be treated with ultraviolet, but not all of UVs are good for you, there are UVA, UVB and their sub-spectrums. The only good for health UV is UVB with a narrow peak at 310nm wavelength. Those tanning beds for bronze effect are wide band UVA+UVB and not good at all neither for vitamin D, nor for your health in general.
So I had bought a UVB 310nm medical lamp, shaved my head, and started using UVB since june, it's been a half year experiment on myself. I started with long, over 10 minute sessions to figure out a limit where I do get burned (>10 minutes). Later I reduced down to 5 min, two times a week, and almost haven't used UVB recently. I don't have vitamin D blood meter, my criteria is a state of my skin, i.e. absence of pain on palpation, less itching, no bleeding sores, no reddening. Looks like UVB works for me, what I can tell from my experiment.
In comparison with sun, UVB lamp with timer showed to be more safe, IMO. Three hours outdoors w/o sunscreen gives a sunburn very likely; but a 5 min/day UVB lamp exposure seems to be safe.
I have a few tiny colored skin patches over body, didn't cover them or anything, just ignored them; they have become less distinguishable after UV. However, if you have patches like birthmarks, you must track their borders. When borders become blurred, that's a not good sign, you gotta them checked by your dermatologist. I think there could be some app to track colored skin patches, there is a bunch of open source libs for that[1].
[1] https://github.com/search?q=skin+cancer