If you have psoriasis like I do, you may have noticed that it tends to get better during the summertime, and worse during the winter. This is probably because you’re out more in the sunlight with shorts, short sleeve shirts or even your bathing suit on. For many of us with psoriasis, the more we’re out during the summer, the itchy, scaly patches tend to get better and less bothersome.

A recent study even noticed that the prevalence of psoriasis in children and adolescents is less in southern California, with the assumption that their increased sunlight exposure can contribute to this.

So why is this?

What Is Psoriasis?

Psoriasis on the arms of a woman
Before we jump into the guts of this, what exactly is psoriasis anyway?

Psoriasis is thought to be a hereditary disease that you get from one or the other (possibly both) parents. I got mine because my father had it, and before him, his mother did.

It’s an autoimmune disease which means that your body attacks itself from the inside.

“Auto” means “self”, like an autobiography is a biography about yourself.

The “immune” portion of “autoimmune” is referring to our T cells or a type of white blood cells that are supposed to keep out foreign invaders, like bacteria.

There are many types of autoimmune diseases including psoriasis, vitiligo, alopecia, rheumatoid arthritis, celiac, multiple sclerosis, lupus and others.

In the case of psoriasis, the T cells attack a lower layer of the skin as if our skin was a foreign invader, which of course it’s not. This causes raised, red, itchy patches which can appear anywhere on the body (yah, even there).

The word psoriasis literally means itchy condition in Greek. OMG, it is that, in spades!

How Does Sunlight Help Psoriasis?

When we get sunlight exposure, the ultraviolet light causes our skin to manufacture vitamin D. It’s the only real natural source of vitamin D, which by the way, isn’t really a vitamin at all.

Vitamins are essential chemicals that our bodies need that they can’t manufacture themselves – we get them by eating other things like plants. Because our bodies manufacture vitamin D, it’s considered a hormone instead.

It’s not well understood, but somehow, when the body produces vitamin D, it helps psoriasis to heal, as well as other diseases such as vitiligo and alopecia.

The sun’s rays during the winter months are less direct, so even if we’re out during that time of year, we get less exposure, and thus our bodies produce less vitamin D. Because the winter months are colder, we also tend to stay indoors more, which of course turns into less exposure, and you got it, less vitamin D again.

Blood serum levels of vitamin D
Those of us with autoimmune diseases like psoriasis also tend to have lower levels of vitamin D naturally and/or use it less efficiently, and over one billion people worldwide are considered vitamin D deficient.

In my own case, I asked my doctor to authorize a vitamin D blood test to see where I was. Their normal limits are between 20 and 79 ng/mL, and they define the various levels as:

  • Deficient <12 ng/mL
  • Insufficient 12-19
  • Sufficient 20-79
  • High 80-150
  • Toxic >150

In my case, I was at a dismal 10 ng/mL, which was WAY below what I should be at (see chart)!

Does Oral Vitamin D Help Psoriasis?

The short answer, is yes, it is one factor that can certainly help. There have been multiple studies that show that oral administration of vitamin D3 can improve psoriasis, and even in its sister disease, psoriatic arthritis.

Where can you get vitamin D?

There are several sources, including:

  • Sunlight (as we already mentioned)
  • Artificial “sunlight” or ultraviolet light boxes – some dermatologists have a UVB lightbox that you can use (for a fee of course)
  • Consuming cold water fatty fishes such as salmon, tuna, sardines, and mackerel can provide some level of vitamin D
  • Most milk in the USA is vitamin D fortified – but you gotta drink a LOT of milk though…
  • Vitamin D3 oral supplements
  • Vitamin D derivative topical ointments and creams (requiring a prescription from your doctor)

The problem with most of those sources is that it’s difficult to get a consistent and meaningful dose that would make a significant difference. For instance, where I live, it’s often too hot to lay out in the sun during the summer and too chilly in the winter, so it’s just not an option for much of the year.

Oral vitamin D3 supplementation was the best way to go.

If you notice in my blood serum levels, I was severely deficient in vitamin D. Based on that, my physician offered to give me a prescription for a once-per-week high dose of oral vitamin D3, but I opted to just take it daily at a lower dose. That way I didn’t have to remember it once per week (I’m bad about that).

He required that I get tested every few months to make sure I didn’t over shoot the safe levels, which you can see I did by just a bit. Adjusting things brought it back down to the “high normal” level, which is where we wanted it.

I did notice that over time, my psoriasis did improve. It’s not a cure by any means (there is NO cure by the way). But that in combination with some other steps I’ve taken, I’ve gotten my psoriasis almost under control.

Note: This article should not be interpreted as medical advice or serve as license to take megadoses of vitamin D, as this strategy has not been studied for long-term adverse effects. Vitamin D supplementation should be performed only under the supervision of a licensed medical physician, dosed according to lab levels, and ideally balanced with other fat-soluble vitamins.

That means don’t do this without talking to your doctor, umkay?