Have you ever noticed how plastic items that are new are generally flexible but old plastic items break easily because they have become hard and brittle? You may also remember vinyl tile flooring of a few decades ago that shrank as it aged, so that the once tight joints gradually became larger and larger. New clothes made with man-made fabrics are strong, soft and flexible but as they age they become more stiff and are much easier to rip.
This is because plastic contains plasticisers and those plasticisers gradually migrate to the surface and evaporate off into the air. The plasticisers are chemicals that are included in the mix when making plastic raw materials for processing into all manner of objects for use in modern life. This includes a wide range of fibres that are further processed into threads to be woven into fabric to make clothing.
The plasticisers are chemicals that are good for plastic but bad for any living body. Man-made fibres put those fabrics on the outside of your body. On cool days this may not do you much harm, if any. Any plasticisers that are released might simply evaporate off into the air. In hot weather this changes because you will start to perspire. The warmer temperature will also increase the rate of release of the plasticisers from your clothing. Your skin becomes moist with sweat, which absorbs plasticiser from the fabric and you soon have a chemical solution on your skin.
Imagine that you are out jogging, cycling or exercising at the gym, in sexy tight stretch clothing made from man-made fabrics. Everything that you are wearing is pulled tight against your skin and is flexing with every movement of your body, like a second skin. Your own skin is oozing salty liquid in the form of sweat. Your second skin is soaked in that liquid and is itself releasing chemical plasticisers into that liquid, helped by the increasing temperature both from your body and from the environment. The water evaporates off but the salt and chemicals stay behind, gradually strengthening the mix until you have a concentrated salty chemical soup being rubbed against your skin by the fabric.
With psoriasis (and many other skin conditions) your skin is affected by what is contacting it from the outside. It is adversely affected by many chemicals. In the scenario described above you have toxic chemicals that are not only in contact with the psoriasis but they are being artificially held there by the fabric and the fabric is also rubbing it into the surface. This is a bad situation for any skin problem.
Here are clothing principles that help to keep psoriasis to a minimum.
1) Check the labels before buying any item of clothing. Stay with natural fibres wherever possible. That means buying mostly cotton or wool articles. Some fabrics are a combination of polyester and cotton, try to keep the polyester to a very small percentage.
2) Make sure that any underwear worn is cotton and not polyester.
3)Loose underwear is less likely to aggravate perspiration than tight-fitting versions. Your skin needs to breathe so that it is cooler and perspires less.
4) Loose outer garments are also better, for the same reasons. They are not held against the skin to trap moisture but allow it to evaporate off.
5) If you must wear man-made fabrics for some reason, such as a sports uniform, get out of it as soon as you can, shower to wash away any perspiration and dress in natural fibre clothes.