# Surf Skin Lab

> Skin barrier physiology for people who spend their lives outdoors in cold, wet and windy conditions. What the stratum corneum is, what raises transepidermal water loss, and what cold air, wind, salt water, occlusion and friction do to the structure. Published by Northbank Media.

## How this publication works

- We name no brand and no product anywhere. Ingredient classes are described by function only.
- There are no affiliate links, no advertising and no sponsored articles.
- We do not diagnose and we do not suggest treatment. Every relevant article carries a referral line to a pharmacist, a GP or emergency services.
- We publish no percentages, measured values, thresholds or quantities, because we have measured nothing.
- Every framework of our own is labelled as ours and stated not to be a measurement or a study result.
- Sun protection is not our subject. It is covered properly elsewhere and appears here only in passing.
- The paid register is alphabetical, labelled as paid, and is not a ranking or a clinical endorsement. We have assessed nobody.

## Structural devices

- Stressor and response: a physical load, what it does to structure and to water loss, how long it persists, the control that acts on that mechanism, and what that control does not fix.
- Layer view: an inline cross section drawn per article showing where in the skin a process happens.

## Sections

### The barrier: https://www.surfskinlab.co.uk/barrier
What the stratum corneum is made of, why transepidermal water loss explains most of what outdoor people feel, the three ways a barrier fails, and how long it takes to rebuild.

- [What the skin barrier actually is](https://www.surfskinlab.co.uk/barrier/what-the-skin-barrier-actually-is): The skin barrier is not a coating and it is not a film you can buy. It is the stratum corneum, the outermost layer of the epidermis, built from flattened dead cells filled with keratin and h
- [Transepidermal water loss, and why it explains almost everything](https://www.surfskinlab.co.uk/barrier/transepidermal-water-loss-explained): Transepidermal water loss is the continuous, unavoidable movement of water from inside the body out through the skin, separate from sweating. It is driven by the difference in water vapour p
- [What barrier damage actually means, physically](https://www.surfskinlab.co.uk/barrier/what-barrier-damage-actually-means): Barrier damage is not one thing. There are three physical failures: surface cells removed by abrasion, lipid sheets between the cells disordered or dissolved, and the water attracting molecu
- [The barrier repair cycle, and how long it actually takes](https://www.surfskinlab.co.uk/barrier/the-barrier-repair-cycle): The outer layer of skin is rebuilt from below, continuously. New cells are produced at the base of the epidermis, mature upward, load themselves with keratin and water attracting molecules, 
- [Sleep, recovery and the barrier's repair window](https://www.surfskinlab.co.uk/barrier/sleep-recovery-and-skin-repair): Overnight is the most useful window for barrier recovery, for two ordinary reasons. Skin temperature rises and water loss through the skin is generally higher in the evening and overnight th
- [Surface pH, and what washing actually changes](https://www.surfskinlab.co.uk/barrier/surface-ph-and-what-washing-changes): The surface of intact skin is mildly acidic, and that acidity is not cosmetic. Enzymes that organise secreted lipids into ordered barrier sheets work best at low pH, and enzymes that dissolv

### Cold, wind and dry air: https://www.surfskinlab.co.uk/cold
Absolute against relative humidity, why a heated room in January is harder on skin than the beach it came from, what wind does mechanically as well as evaporatively, and where cold responses stop being ordinary.

- [Cold air is dry air: the physics behind winter skin](https://www.surfskinlab.co.uk/cold/cold-air-and-absolute-humidity): Air can only hold so much water vapour, and how much depends steeply on temperature. Cold air at full saturation contains a small absolute quantity of water. Warm that air up without adding 
- [Why winter indoors is often worse than winter outdoors](https://www.surfskinlab.co.uk/cold/why-winter-indoors-is-worse): A heated building in winter takes cold air that holds very little water and warms it without adding any, so its relative humidity falls sharply. Combine a large vapour pressure gradient with
- [Wind: evaporative and mechanical stress in one exposure](https://www.surfskinlab.co.uk/cold/wind-as-a-mechanical-stressor): Wind attacks the barrier twice. It strips the still, locally humid boundary layer from the skin surface, holding the vapour pressure gradient at maximum for the whole exposure, which raises 
- [Hand skin in cold water, and why it recovers so slowly](https://www.surfskinlab.co.uk/cold/hand-skin-in-cold-water): Hands do badly in cold water for four reasons that stack. The palmar skin has a very thick outer layer that, once it dries and stiffens, fails by deep cracking rather than by flaking. Surfac
- [Cold related skin responses, described and referred](https://www.surfskinlab.co.uk/cold/cold-related-skin-responses): Skin responds to cold in several recognised ways. Some are ordinary physiology: reduced surface blood flow, then reactive flushing on rewarming, and stiffness because cold tissue is less pli
- [Windburn: three mechanisms with one appearance](https://www.surfskinlab.co.uk/cold/windburn-and-what-it-actually-is): Windburn is a folk term, not a diagnosis. A face that is red, hot, tight and sore after a long outdoor exposure can be the result of rapid water loss from a stripped boundary layer, mechanic

### Water and immersion: https://www.surfskinlab.co.uk/water
What repeated salt immersion does to the outer layer, why fresh water is the harsher soak, why the wet and dry cycle costs more than either state, and what hours inside neoprene do to skin.

- [What repeated salt water immersion does to the stratum corneum](https://www.surfskinlab.co.uk/water/salt-water-and-the-stratum-corneum): Salt water immersion does three things to the outer layer of skin. It floods and swells the corneocytes, forcing them apart and disrupting the lipid sheets between them. It rinses out the sm
- [Fresh, salt and treated water compared, briefly](https://www.surfskinlab.co.uk/water/fresh-salt-and-treated-water-compared): Three waters, three mechanisms. Fresh water swells the outer cells most, because the concentration difference across the cell is largest, and it rinses out the water attracting molecules ins
- [Wet and dry cycling: why the cycle costs more than either state](https://www.surfskinlab.co.uk/water/wet-and-dry-cycling): Repeated wetting and drying loads the outer layer mechanically. Each wetting swells the cells and pushes them apart; each drying shrinks them again and pulls the lipid sheets between them. T
- [Neoprene and occlusion: skin held wet and warm for hours](https://www.surfskinlab.co.uk/water/neoprene-and-occlusion): Occlusion means the skin is covered by something that prevents evaporation. Under a wetsuit, the outer layer stays fully hydrated for hours, which softens it progressively and makes it fragi
- [Showering after a session: temperature, length and what to skip](https://www.surfskinlab.co.uk/water/showering-after-a-session): The post session shower is the most adjustable event in an outdoor day and the one most likely to be doing harm. Hot water mobilises the lipids between your outer cells and removes more of t
- [Hard water, surfactants and why the same wash behaves differently](https://www.surfskinlab.co.uk/water/hard-water-surfactants-and-residue): Hard water contains dissolved calcium and magnesium salts. With traditional soap those ions form insoluble residues that deposit on skin and fabric, which is why hard water areas need more p

### Friction and mechanics: https://www.surfskinlab.co.uk/friction
Load, friction coefficient, sliding distance and the state of the layer. Seams, collars, fissures, lips, scalp and the blade you draw across a face that has already had a hard week.

- [Friction, rash and chafe as mechanical problems](https://www.surfskinlab.co.uk/friction/friction-rash-and-chafe): Chafe is a mechanical failure. Two surfaces move relative to one another under load, energy goes into the interface, and the outer layer of skin loses cells. The variables are the load press
- [Seams, collars and pressure points: finding the one that is doing it](https://www.surfskinlab.co.uk/friction/seams-collars-and-pressure-points): Recurring marks, rashes and raw patches almost always trace back to one contact, and the outline of the mark tells you which. A strip means a seam. A ring means a seal or a strap. A patch at
- [Chapped lips, and the physics of why lips are different](https://www.surfskinlab.co.uk/friction/chapped-lips-and-why-lips-are-different): The vermilion of the lip has a very thin stratum corneum, effectively no sebaceous glands and no sweat glands, so it has neither a thick barrier nor a surface lipid film of its own. Water lo
- [Cracked hands: the mechanics of a fissure](https://www.surfskinlab.co.uk/friction/cracked-hands-and-fissures): A fissure is a crack that propagates through a stiff, dry stratum corneum under tensile load, which for a hand means every time it closes or grips. It hurts disproportionately because the sp
- [Scalp and hair under salt, wind and a hood](https://www.surfskinlab.co.uk/friction/scalp-and-hair-under-salt-and-wind): Hair and scalp fail differently and need separating. Hair is dead keratin with a cuticle of overlapping scales; salt crystals and mechanical handling lift and chip those scales, which is why
- [Shaving and grooming on skin that has already had a hard week](https://www.surfskinlab.co.uk/friction/shaving-on-stressed-skin): Shaving is controlled abrasion. A blade drawn across skin removes the top of the stratum corneum along with the hair, which is why skin stings afterwards and why a good shave feels smooth. O

### Materials and routine: https://www.surfskinlab.co.uk/materials
Occlusives, humectants and emollients as three different jobs. What labels do and do not mean. And the five minutes after a session, ordered by benefit per second spent.

- [Occlusives, humectants and emollients: three different jobs](https://www.surfskinlab.co.uk/materials/occlusives-humectants-and-emollients): Occlusives sit on the surface and slow evaporation. Humectants attract and hold water, drawing it from the air when the air is humid and from the layer below when it is not. Emollients fill 
- [The ingredient classes that support barrier repair, by function](https://www.surfskinlab.co.uk/materials/ingredient-classes-that-support-repair): Beyond the three basic jobs, a small number of ingredient classes have a defensible functional rationale in barrier care: lipid components matching those found between the cells, small water
- [What fragrance free and hypoallergenic actually mean](https://www.surfskinlab.co.uk/materials/fragrance-free-and-hypoallergenic): Fragrance free generally means no ingredient has been added for the purpose of imparting a scent, which is a meaningful statement, though products can still smell of their ingredients and th
- [Patch testing as a self care practice, and what it is not](https://www.surfskinlab.co.uk/materials/patch-testing-as-a-self-care-practice): Two different things share this name. Clinical patch testing is a diagnostic procedure carried out by a healthcare service, in which standardised allergens are applied under occlusion and re
- [The car park routine: what to do when you are cold, tired and not at home](https://www.surfskinlab.co.uk/materials/the-car-park-routine): The five minutes after a cold session decide most of what happens to your skin, and they are usually spent badly because you are cold and in a hurry. The order that matters is: rinse the sal
- [Field care for lips and hands: what to carry, and when it is worth using](https://www.surfskinlab.co.uk/materials/field-care-for-lips-and-hands): Lips and hands cause most of the winter trouble for the same two reasons: they are the most exposed and the least self supplied. Lips have effectively no sebaceous glands, and palmar skin ha
- [Reading an ingredient list by function, not by brand](https://www.surfskinlab.co.uk/materials/reading-an-ingredient-list-by-function): An ingredient list is ordered by decreasing concentration down to one per cent, after which order carries no information. That single rule tells you most of what you need: what is at the top

### Limits and referral: https://www.surfskinlab.co.uk/limits
The boundary of this publication, stated once and kept to. When to see a pharmacist or a GP, what an occupational skin problem changes, how to read a claim, and what we refuse to do.

- [When to stop reading and see a pharmacist or a GP](https://www.surfskinlab.co.uk/limits/when-to-see-a-pharmacist-or-gp): Everything on this site describes normal skin under environmental load. The boundary is crossed when skin is broken and not closing, weeping, crusting, spreading, hot, swollen or increasingl
- [Occupational skin for people who work outdoors and in water](https://www.surfskinlab.co.uk/limits/occupational-skin-and-outdoor-work): Work related skin problems are recognised in Britain as a preventable occupational health issue. The Health and Safety Executive publishes guidance for employers and workers on skin at work,
- [Reading skin claims critically, including ours](https://www.surfskinlab.co.uk/limits/reading-skin-claims-critically): Most claims about skin fail on one of four points: they describe a mechanism that does not exist, they attach a number nobody measured, they generalise from a study that did not test what is
- [What this publication will not do, and why that is the point](https://www.surfskinlab.co.uk/limits/what-this-publication-will-not-do): We will not name a brand or a product, recommend anything you can buy, carry an affiliate link, run advertising, diagnose, suggest treatment, invent a number, repeat a claim we cannot suppor

## Reference pages

- About and funding model: https://www.surfskinlab.co.uk/about
- Editorial standards: https://www.surfskinlab.co.uk/editorial-standards
- The paid register: https://www.surfskinlab.co.uk/register
- Register criteria and rates: https://www.surfskinlab.co.uk/register/criteria
- Newsletter and sponsorship rate card: https://www.surfskinlab.co.uk/newsletter
- Privacy: https://www.surfskinlab.co.uk/privacy