Out of all the success stories collected on this website up to now, this might be the most surprising yet efficient approach to curing seborrheic dermatitis. I will start by reproducing this post:
I had quite bad seborrheic dermatitis over the last 2 years (I’m 28, male, white, British). I’ve had it earlier in my life too but it was at its worse. Red rash all over my temples, cheekbones and creeping onto my forehead and near my nose. I seemed to clear up periodically then come back, and I couldn’t isolate the variable that caused this. I suspected many things: hot baths/showers (dehydrate the skin), sweating, fatty foods, shampoo/soap, germs in the shower head, germs from hands, bed linen, air pollution, central heating (de-humidifying the air), lack of vitamin D, acid rain, some unknown allergy. But what I’m fairly sure it boils down to is exposure to sunlight.
I think the dynamic is this: our bodies (over)produce sebum around the scalp and face area. There is a yeast which grows on the skin when sebum is present, and the chemical reaction it produces causes inflammation of the skin, so you face looks all red. Put simply, ultraviolet light from the sun kills off the yeast before the inflammation begins. If you go extended periods without much exposure to sunlight, the process will continue unhindered.
I’m fairly confident about this explanation because now that I know that sunlight is the key variable, I can measure the effect to some extent. Over the last 2 years I’ve been doing an office job which began at 6.30am and ended after 5pm, sometimes later. That could mean no daylight except during a brief walk to grab some lunch. Plus, some weekends I would travel to my parents house by train (few mins walk to the station at each end), and then spend most of the time just relaxing indoors (since I didn’t need to go out for food, and in Scotland the weather is usually atrocious). I was severely deprived of direct sunlight. It’s no wonder seborrheic dermatitis could spiral out of control. Conversely, it always seemed to clear up when i went on holiday and walked out all day in the sun for a week or two. Nowadays if I go over 24 hours staying mostly indoors (eg in long haul flights), I can practically feel it subtly setting in.
I know at one point I was overproducing sebum, like I could feel it in my hair and it was even forming this yellowish substance behind my ears. This seems like a slightly separate issue but one that compounds seborrheic dermatitis. When I played sport, I think the sebum would pour down from my scalp and get all over my face, and this tended to coincide with it getting worse. So now I occasionally use coal tar shampoo, which stops that problem.
I tried many things to help before, like moisturisers and vitamin supplements. The long term solution is sunlight (for me at least). The only other ‘treatments’ I’ve found to help even slightly are: coal tar shampoo (as mentioned above), salicylic acid (eg. Johnson&Johnson’s bottles) to cleanse your face with using cotton pads (not every day, just if it’s getting bad), hydrocortisone (HC45, if you see a red patch starting, can sometimes stop it), and ‘exfoliant’ (e.g. Dead Sea Magic Spa mild exfoliant; helps get rid of the top layer of dead skin). But honestly I wouldn’t bother with any of these, just get yourself lots of sunlight.
My skin has been clear for at least 6 months now. It will be interesting to see if I can keep it clear over the winter months, by deliberately seeking more sunlight exposure. I can post before/after pics if anyone wants to see how bad I was before. I hope this works for other people and not just me: I guess you have to ask yourself do you spend enough time outdoors during the day? Overcast weather and smog may also be a hindrance even if you do.
The same user in a later post confirms his hypothesis:
Just to give an update: my seb-derm only came back for about a week in the last 12 months, which was the middle of January. That coincides with the worst weather and daylight hours. Soon as it started getting bright when I walk to work in the morning it cleared up and hasn’t been back at all since. If I’m only going to suffer from this condition a few days per year (i.e. when it’s actually noticeable to others) I can live with that!
What does science say?
The scientific studies do not directly talk about daylight as a cure for SD, but there’s a number of papers that confirm the correlation between SD and daylight exposure. For instance, this paper finds that
The prevalence of outpatients with SD has now been found to be directly related to the number of gloomy days in the area. Since UV light might not be the only reason for the well-known improvement in SD in summer, an explanation possibly related to melatonin is envisaged.
Another study looks at the seasonal variation of seborrheic dermatitis. Here is the bar chart containing the proportion of annual dermatologic visits in each season (as reproduced from the paper):
As expected, SD-related visits are much less frequent in the summer and increase significantly in the darker seasons. The authors also compare SD to other skin conditions in the table below:
Finally, this study concludes:
The course of SD is seasonal. Possibly because of variations in temperature and humidity, the condition worsens during fall and winter and improves in summertime. Outpatients with SD clearly diminish in number in July and August in parallel with the increasing duration of daylight. Sunlight is regarded as a positive factor by the patients themselves and is related to the germicidal effects of UVB on P. ovaIe [note: P. ovale or Pityrosporum ovale is another name for Malassezia); however, SD also improves on the scalp, where UVB cannot reach. Other wavelengths may therefore be important or daylight may work through a systemic mechanism. Hypotheses concerning the role of daylight in melatonin suppression have been advanced.
It is important to note that long-term exposure to high doses of UV light can also have negative effects such as skin cancer and immunosuppression. The latter is known to be a factor for SD (exemplified by the fact that HIV patients have a much higher incidence rate of SD). This study looked at the prevalence of SD in mountain guides who have a high occupational exposure to solar UV radiation. Forty-six of 283 (16. 3%) mountain guides when examined clinically were found to have SD. Thus, SD affects mountain guides in a clearly higher percentage than the general population. The authors suggest UV-induced immunosuppression due to occupational sun exposure as a pathogenetic factor.
Takeaways
The scientific literature supports the hypothesis of daylight being helpful for SD. Unfortunately the exact mechanisms are not well understood (yet).
One explanation could be the fact that the ultraviolet rays of the sunlight are killing the malassezia yeast (thought to be responsible for causing SD). However, there are other variables that are highly correlated with the warm seasons. When it is warmer, one tends to sweat more, to spend more time outdoors, to be more active. Also the saturated fats in the skin’s pores become more fluid and tend to be eliminated faster (instead of being stored there and feeding the yeast. All these might also play an important role in clearing up the SD.
In the meantime, make good use of this information. Spend time outdoors, get some sunlight (consider a UV lamp at home or a tanning salon in the winter), be active, move your body. Finally, a cautionary note: although sun exposure seems to improve SD, this should be done with care in order to avoid increasing the risk of skin cancer or suppression of the immune system.
Share your experience
Help the SD community by sharing your own experience regarding the effect(s) of daylight on your skin in the comments below.
3 Comments
Pingback:
Pingback:
Pingback: