This is the last of Skin Facts series and as we come to a close in 2015 and usher in 2016, one Skin Fact to look at is how our skin renew itself. The dermatological terms are ‘epidermal cell proliferation‘ which takes into account the turnover of cells and there are differences between normal adult, baby and eczema skin. Here’s a look at Skin Renewal Facts!
Basics of Skin Renewal
Skin Renewal in Baby and Eczema Skin
The skin regenerate itself every 27 to 39 days, meaning that the cells from the lower layer of the epidermis (outer layer) move up to the surface and differentiate. The epithelial cells are called keratinocytes and they have different structures within the different layers of the epidermis (from the deeper basal layer, to spinous, granular to the corny layer at the surface). The top layer is also known as the stratum corneum, for which we have looked into the transepidermal water loss through stratum corneum.
This skin renewal is not related to wrinkles as wrinkles are primarily due to the loss of collagen, which is in the dermis (middle layer) of skin. Baby skin feels ‘softer’ and more elastic likely due to shorter collagen fibres.
Baby Skin – Cell Turnover Rate
Microscopic examination of baby skin showed that baby stratum corneum is 30% thinner than adult skin, and that baby epidermis is 20–30% thinner than adult skin. The cell size at the corny layer of the baby skin is smaller, which implies that the baby’s cell turnover rate is higher. This correlates with better wound healing in infant skincompared to adult skin. Epidermal cell proliferation rate decreases with age.
Eczema Skin – Defective Protein
As cells proliferate, there are proteins that are expressed by the skin cells. Studies have been made on various proteins and one of the most distinguishing (lack of) proteins is that of filaggrin (FLG), which serves to produce and protect the skin barrier. In people with eczema, there is lower level of FLG, resulting in flatter skin surface cells, disrupted protective fatty layer, reducing the moisturizing function of the skin and increasing water loss from the skin. Reduced FLG also increases the skin pH and leads to increased skin inflammation. It is possible that for eczema skin, the defective protein expression makes it unable to proliferate but instead ‘terminate’ at the basal layer. This has the effect of weakening the skin structure.
This is the 6th post exploring ‘Skin Facts’ and today’s focus is on the lipids/ fats in our skin. There is distinct difference between the skin lipids of normal adult skin, baby skin and eczema skin. Let’s explore skin lipids!
Types of Skin Lipids
Skin Facts – Lipids in Baby and Eczema Skin, and its functions
There are lipids from both sebaceous and keratinocyte/ epidermis:
Sebaceous – from sebaceous glands and coats the skin surface, mainly triglycerides, wax esters and squalene, fatty acids and smaller amounts of cholesterol, cholesterol esters and diglycerides
Epidermal – found between the epidermal skin cells, mix of ceramides, free fatty acids and cholesterol
Lipids from Sebaceous Glands – Sebum
The concentration of sebum is higher at the forehead, face, scalp, upper chest and back and lower on the hands and feet and none on the palms and soles.
Function of Sebum
Deliver antioxidants to the surface of the skin in the form of vitamin E
Increased protection via increasing impermeability of skin
Maintenance of skin moisture content
Eczema and Lipids
Atopic dermatitis is associated with reduced epidermal lipids in all three categories – reduced ceramides, cholesterol and free fatty acids
The lack of lipids lead to a weak ‘brick and mortar’ structure where the lipids are akin to the mortar that keep the skin cells (bricks) together. This weakened skin barrier is associated with increased transepidermal water loss and increased skin permeability
The subcutaneous fat in baby skin is rich in the saturated oils – palmitic and esteric acid, with the following characteristics:
Higher melting point temperatures – freeze more easily (such as eating ice or popsicle for hours!), thus avoid extreme temperature for babies
Saturated vs Higher unsaturated oleic acid and linoleic acid in adults
Infant skin contains less total lipids compared to adults
Malnutrition is linked with changes in surface lipids, where an alteration in skin lipids has been observed due to essential fatty acid deficiency
With a lower lipid skin content, it is important not to excessively wash baby skin and further remove the skin lipids.
Other posts on EczemaBlues.com on skin lipids are:
Eczema News – ‘Lipid fingerprint’ Treatment Approach : Where the Oregon State University is developing a system to identify the missing lipids in an individual skin, thus the possibility of getting moisturizer to replenish the specific deficient lipid.
Many chemicals come into contact with our skin, some intentional and others inadvertently. How much chemicals penetrate our skin?What about that of a baby or those who have defective skin barrier like eczema sufferers? This 5th post of Skin Facts series explores the chemicals our skin comes into contact with.
Our Skin Structure – How do Chemicals Penetrate?
Chemicals definitely penetrate certain layers of our skin, otherwise, the skincare industry will collapse if all skincare products just stay on the skin surface and no product can claim to improve your skin! Chemicals penetrate different layers of skin barrier (that’s part of the ‘price’ we pay for a skincare product where technology is involved to enhance penetration).
Here are 3 Ways Chemicals Penetrate our Skin:
Penetration/ Transcellular absorption – via the stratum corneum through the corneocytes (flattened cells that made up the horny layer); Stratum corneum contains about 40% protein (primarily keratin), 15% to 20% lipids and 40% water.
Intercellular absorption (main route) – Chemical is transferred around the corneocytes in the lipid-richextracellular regions; Lipids present in the intercellular spaces of the stratum corneum are by weight: 45–50% ceramides, 25% cholesterol, 15% long-chain free fatty acids and 5% other lipids, the most important being cholesterol sulfate, cholesterol esters, and glucosylceramides.
Michaels et al. (1975) is the one who came up with the ‘brick and mortar‘ analogy describing corneocytes filled with lipids. Dermatologists explain eczema skin has the wall without strong mortar holding the bricks.
Appendageal absorption – Chemical bypasses the corneocytes, entering the shunts provided by the hair follicles, sweat glands, and sebaceous glands
Baby Skin – More Chemical Penetration?
Chemical Penetration in Our Skin and Our Children
The baby skin is not fully developed, where Infant stratum corneum was found to be 30% thinner and infant epidermis 20% thinner than in adults. More chemicals penetrate due to this and there’s higher risk associated with this penetration due to:
High surface-area to volume ratio
Higher metabolic rate, higher respiratory volume
Immature drug metabolism, drug carriage and detoxification systems
Decreased subcutaneous fat stores that (i) increase absorptive area and (ii) decrease the volume of distribution of the chemical
Higher chances of injured skin (for instance, from adhesive tapes) increase skin permeability
Vulnerable to endocrine disrupters
Eczema Skin – How Defective Skin Barrier Affect Chemical Penetration
Eczema skin is defective which allows more chemicals to penetrate and be absorbed with possible effects of:
Enhanced absorption of a specific chemical
Entrance of larger molecules such as proteins and nanoparticles
Facilitate entrance of chemicals into and through the skin
The Care in Chemicals
With increased chemical penetration, it follows then that we ought to be extra careful of what goes onto baby skin as well as eczema skin (and baby’s eczema skin!). It is impossible (and not necessary) to aim for zero chemical contact, instead know which types of products not to use and what skincare/ cosmetics ingredients to avoid:
Soap – Avoid as it is drying (due to alkalinity) and harsh for skin; alternative: use a gentle cleanser/ bath oil/ oatmeal bath
Anti-microbial wash – Avoid; read this post to learn more about effects of anti-microbial wash and its ingredients that irritate skin
Shampoo – Choose one without key irritants (see below)
Antiperspirant – Safe to use, can opt for an aluminium and paraben free one (see WebMD article)
Skincare moisturizer – Choose one without key irritants (see below)
Detergent and detergent residue on clothes – Use a hypoallergenic one and turn on a longer cycle (see this post)
Toothpaste – Safe to use, just don’t overuse
Baby wipe – Choose one without Methylisothiazolin (MI) and fragrance free (see this post)
Bubble bath – Avoid as the average bubble bath is irritating to skin
Cosmetics – Throw away expired cosmetics
Instead of trying to eliminate all chemicals, it’d be more practicable to avoid ingredients that are known irritants or suspected to cause harm:
AVOID #1 Perfume
Fragrance, phthalate esters, synthetic musk compound, Benzyl alcohol, scent, aroma, Abietic acid, alcohol, Abitol (see this post on various names of perfumes)
“The average fragrance product tested contained 14 secret chemicals not listed on the label,” reports EWG, which analyzed the Campaign’s data. “Among them are chemicals associated with hormone disruption and allergic reactions, and many substances that have not been assessed for safety in personal care products.” EWG adds that some of the undisclosed ingredients are chemicals “with troubling hazardous properties or with a propensity to accumulate in human tissues.” Examples include diethyl phthalate, a chemical found in 97 percent of Americans and linked to sperm damage in human epidemiological studies, and musk ketone, which concentrates in human fat tissue and breast milk. Fragrance secrecy is legal due to a giant loophole in the Federal Fair Packaging and Labeling Act of 1973, which requires companies to list cosmetics ingredients on the product labels but explicitly exempts fragrance.”
I find it interesting because if you look at your perfume, even the most expensive ones, you would find many of them are irritants and definitely hard to pronounce! There are also ingredients that are ‘hidden’ behind proprietary names given by the brand.
Consequence: Irritate, allergenic, allergic rhinitis, chronic sinus, asthma, accumulate in the environment, the body and the breast milk, disrupt the endocrine system (Endocrine system is a network of glands that produce and release hormones).
1,2 Propanediol, 1,2-dihydroxypropane, methyl glycol, trimethyl glycol (Ethylene Glycol is more toxic than propylene glycol)
Found in: Skincare products, shampoo
Consequence: Known irritant for babies, infants and those with sensitive skin conditions such as eczema, or those with prolonged dermal contact e.g. during treatment of burns
Found in: Shampoos, conditioner, bath additives, toothpaste, baby wipes
Consequence: Irritant and drying to skin, corrodes hair follicle and impedes hair growth
Here’s what I learned from dermatologist Dr Cheryl Lee on surfactants used in our product (see post):
Surfactants are designed to remove dirt and oils from the skin, but the problem is that they can also remove the lipids from the skin as well. This leads to disruption in the skin barrier and exacerbates all the skin barrier problems in atopic dermatitis…Of note, a recent study by Belsito et. al., showed that the surfactant cocamidopropyl betaine (CAPB) is more likely to cause allergic contact dermatitis in people with atopic dermatitis than in those who do not have atopic dermatitis.
Some of the above chemicals are UV-filters such as oxybenzone that are excreted in the urine after application to the skin. Sun protection is a must, choose a physical blocker type and learn more in Skin Fact – Sun Protection in Adult, Infant and Eczema Skin
Consequence: Biochemical or cellular level changes, disrupts the endocrine system, accumulates in breast milk and in the environment, photo allergic reaction (PABA)
Others to Avoid
Triclosan – Present in shampoos, bath cleansers, toothpast and baby wipes, can cause allergies and bacterial resistance (see this eczema news on household products’ exposure)
It is studied that twice daily moisturization with a hypoallergenic (meaning no fragrances, no essential oils, no plant extracts, no formaldehyde-releasing preservatives, no lanolin, no neomycin, no bacitracin, no methylchloroisothiazolinone) moisturizer in high-risk newborn babies lead to an approximately 50% reduction in rates of new onset atopic dermatitis.
We have also looked at infants being more susceptible to sunburn. This, on surface, seems to suggest that putting on moisturizing and sunburn is good for the babies but there’s a major caveat that you should not be putting on harmful chemicals since so much more chemicals penetrates infant skin (and possibly even more for infants with defective skin). Use good quality moisturizer, tested safe for babies and without the key irritants AND avoid sun (rather than ‘suntan’ a baby with sunscreen as we’ve seen sunscreen contains quite a fair bit of irritants!).
We have been learning about skin facts and last week, we learnt about insensible perspiration – which is transepidermal water loss that we cannot control. This week we are learning about sweating, sweat glands and how sweat affects eczema skin. First, the basics:
Why, How Much, Where and What of Sweating
Sweat – Why, How much, where and what
WHY – Sweating is a way to cool the body temperature whereby sweat glands in the skin are activated and release sweat. The evaporation of the sweat cools the body and those leftover sweat (on a humid day) leaves you soaked. See #SkinishMom post on sweaty occasions.
HOW MUCH – We sweat different amounts on different occasions; for an hour of exercise, one can sweat from 0.8 to 1.4 liters. Excessive sweating is ‘defined’ in terms of the sweating deteriorating the quality of life, a condition known as hyperhidrosis.
WHERE – This gets interesting as emotional sweating when you’re angry or anxious activate the sweat glands on the palms, soles and underarms! Sweating after eating spicy foods (gustatory sweating) are on the lips and forehead.
WHAT – Sweat is made up of water, ammonia, urea, minerals (like sodium and magnesium), trace metals, lactate and various salts and amino acids. The exact composition of sweat varies depending on diet, genetics and activity level.
Sweat Glands in Adults and Children
Sweat comes from two types of glands:
Eccrine glands – All over the body in the dermis (layer after the outer epidermis of skin), there are over 2 million eccrine glands. The sweat exit via a pore. The sweat from eccrine glands has no smell of its own but the smell comes from bacteria on our skin feeding on the oils in the sweat.
Apocrine sweat glands – At armpits and private parts, and the sweat exit via a hair follicle. Upon puberty, the glands make a thick, oily fluid which has a smell.
Women – More sweat glands then men, but less active
Babies – Babies are born with sweat glands but they are not activated, only the ones on the foreheads are! After the forehead, the sweat glands on the trunk, arms and legs are activated. In this Common Summer Skin Rash series – Heat Rash, dermatologist Dr Robin Schaffran explained heat rash, medically known as miliaria:
Miliaria occurs under conditions of high heat and humidity that lead to excessive sweating. Occlusion of the skin from too much clothing or blankets can aggravate the pooling of sweat on the skin surface leading to over-hydration of the skin. In susceptible persons such as infants who have immature sweat glands, this often leads to transient blockage of the sweat ducts. Therefore, as more sweat is produced, there becomes and inability to secrete the sweat because of the blockage.
Sweat and Eczema
Sweat is known to cause irritant reaction for those with eczema. However, what in the sweat irritates is not known. In the Skin pH series – Moisturizer and Skincare Products interview with dermatologist Dr Cheryl Lee:
As for sweat, the biggest problem is the irritancy of the sweat itself. The salts from sweat can crystalize and act as an irritant to the skin. If you can see that your baby’s sweat has dried and has a salty residue, then I would recommend rinsing it off with plain water (no soap) to prevent it from becoming an irritant.
It could be one of these compounds, the combination of them, the changing pH of the skin, or even the sweat’s water content that can cause the itching and stinging sensations to some people with eczema.
Eczema may also occur in those suffering from ichthyosis, a condition that has excessive skin scales, clogging sweat glands and preventing sweating normally. Pompholyx is another condition that some eczema sufferers also have, with a distinctive appearance of itchy small blisters on the palms of the hands. It is also more closely associated with excessive sweating and can be found on the soles and toes.
This is the third week of ‘Skin Facts’ and last week, we’ve looked into the sun protection function of children vs adult skin, and how the sun affects eczema skin. Today, we’re looking into another critical function of skin and one that is very relevant for eczema skin – our skin’s moisture retention property. One can also view it as how much moisture is lost from our skin, known as Transepidermal Water Loss (TEWL). TEWL is studied by dermatologists, as excessive TEWL points to a defective skin barrier, and in severe cases, affect the ability of the body to function. Let’s go “water deep” into this skin function!
Water and our Body
Water makes up a large point of our body weight, here are some interesting facts about the water in our body from water.USGS.gov (the US Geological Survey website):
Water content in our Body
Lungs 83%
Muscle 79%
Kidneys 79%
Brain 73%
Heart 73%
Liver 71%
Skin 64%
Bones 31%
Percentage of Body Weight that is Water
Fetus 94%
Infant at birth 78%
One-year old 65%
Female 55% (due to higher fat content)
Male 60%
Elderly 50%
Functions of Water in our Body
Forms the building material of cell
Regulates body temperature by sweating and respiration
Transport via the bloodstream
Flushes waste via urination
Absorbs shock for brain and spinal cord, also lubricates joints
Forms saliva
Moisture Loss and Retention from Children, Normal and Eczema Skin
Water Loss from our Skin
Our skin allows water to be lost through it, as part of insensible perspiration (or transepidermal diffusion) and sweating. Insensible refers to us not being aware of it (another insensible loss of water is from respiration). Sweating helps regulate our body temperature, via cooling of the skin. However, sufficient intake of water is required in order for sweating to not dehydrate the body and continue to be effective in cooling our body temperature.
Much of the water is lost through the stratum corneum, the upper most layer of the epidermis made up of a dead cell layer. A defective stratum corneum layer will allow excessive epidermal water loss and potentially, increase risk of irritant and allergen sensitivity. Water loss from evaporation from our skin is about 400ml daily in an adult. For research news on how the skin can be a channel for allergy, see Food Sensitization from Eczema.
Transepidermal Water Loss (TEWL) from Children Skin TEWL from baby skin is higher than normal adult skin, due to their thinner stratum corneum. For premature infants less than 30 weeks, there are also fewer layers of stratum corneum resulting in increase fluid and heat loss. Interestingly, infant skin is found to have higher water content and able to absorb more water but lose excess water faster than adult skin.TEWL was also strongly predictive of AD at 12 months (study here). The natural moisturizing factor (protein breakdown products such as small amino acids, urea, pyrrolidone carboxylic acid, ornithine, citrulline, urocanic acid) in infant is also lower than an adult.
How this Impact Parents Caring for Baby Skin Protection of the stratum corneumis important, and this can be via:
Reduced bathing – Washing baby skin with a washcloth during the first 4 weeks of life is associated with increased TEWL and decreased stratum corneum hydration compared with simply soaking in water. The recommendation is to use a mild liquid cleanser with water (less drying than water alone), and that bathing should be brief (10 minutes or less) and no more than every other day with spot cleaning in between.
Good bathing regimen – Includes not using hot water, not scrubbing the skin dry (but pat dry), keeping it short to 10 minutes, not using soap and moisturizing right after (see video)
Good skincare regimen – Moisturizing protects the skin barrier (see video). It is important to note that given the thinner stratum corneum of infants, their higher surface area to body ratio, infants are more vulnerable to toxicity of products. Therefore, be sure you understand the product label (there’s a comprehensive Sensitive Skin Products blog series to help you with that).
Transepidermal Water Loss (TEWL) from Eczema Skin
TEWL is studied to be higher in eczema skin and also dry skin (without eczema). The water content of stratum corneum is also lower in adults with eczema than normal skin. It is also studied at the natural moisturizing factor of eczema skin is defective, lacking in proteins that are able to play a role in the skin’s humectant property – the ability to pull moisture from the environment and retain this water (which is why 2nd generation moisturizers incorporated humectant property, learn more here).
Drinking Water and Skin
A myth. Dehydration will affect skin but drinking excess water will not lead to ‘glowing’ skin. Drinking enough water will also not prevent skin aging or wrinkles as these are related to genetics, sun and oxidative stress brought on by pollutants. Read this #SkinishMom Investigation! – Drinking water for dry skin
To round-up, we learnt that water is integral to our body and to our skin. We have insensible water loss and a thinner stratum corneum in baby skin and a defective stratum corneum in eczema skin both results in increased transepidermal water loss (TEWL). This knowledge should encourage (not discourage!) us to be more committed to a good bath and skincare routine.
We have started learning skin facts last week, specifically on the skin (surprise) isn’t the largest organ and that well, we don’t really know what’s in our dust. This week, we’re taking up a notch on going ‘intensive’ into the difference in the sun protection function of adult, child and eczema skin.
Normal Adult Skin
Sun Protective Function of our Skin and how it differs for Baby Skin and Eczema Skin
Adult skin has a fully developed sun protection function, in the form of pigment melanin which gives the skin its color. Therefore, the darker one’s complexion, the higher the sun protection. Melanocytes are the melanin-producing skin cells and it is the activity of the melanocytes, i.e. the amount of melanin produced, and not the number of melanocytes that determine the skin color.
When one is exposed to sun, more melanin is produced to help protect the skin against UV rays, thus giving a ‘tan’. Melanin can reduce the oxidative damage caused by UV rays but isn’t able to fully protect from the damaging effects of UV rays (see this news on potential harm of ‘sun-activated’ melanin to our skin).
Children Skin
An infant’s skin has not fully developed in many ways that make a baby more vulnerable to the damaging effects of UV rays – it has less pigment/ melanin, thinner skin/ stratum corneum and a higher surface area to body ratio.
Studies have also pointed to infants with exposure to UV rays will show skin pigmentation on exposed skin from as young as one year old (first summer). This was true even for infants who used sun protection when outdoors but not when in the car, in the shade or on a cloudy day. There are also studies showing that exposure to UV during childhood and adolescence can lead to skin cancer later in life.
Eczema Skin
There is no study that points to differences in melanocytes/ melanin due to eczema. However, the sun is known to both improve and aggravate eczema, for instance:
Some eczema sufferers report improved eczema during holiday when outdoors more often (no study confirmed why holiday seems to improve eczema).
Phototherapy is used as an eczema therapy for adults.
Active eczema flare-up should stay away from the sun as it can worsen eczema, and increase vulnerability to sun burn.
Certain skincare products increase sensitivity to sun, such as those containing ingredients alpha-hydroxy acids (AHAs), beta-hydroxy acids (BHAs), salicyclic acid, glycolic acids, Retin-A and hydrocortisone. Moisturized skin may get sun burn more easily, thus put on moisturizer and wait for 30 minutes before applying sunscreen.
Sun – We need it, but not too much of it.
Our skin play an important role in the synthesis of vitamin D, where vitamin D can increase the production of skin proteins (cathelicidin) and antimicrobial peptide (AMP) which protects against skin infection. However, just 15 minutes a day is enough and it’s referring to getting sun on the face and arms (i.e. no need to be in a bathing suit!). During summer, 2-3 direct sun exposures of 20 minutes per week is sufficient. Short frequent sun exposure is better than long exposure.
Rays from the Sun
There are 3 different rays from the sun:
UVA – 320 to 400 nm : passed through the atmosphere
UVB – 290 to 320 nm : passed through the atmosphere
UVC – 100 to 290 nm : most dangerous, but filtered and do not pass through the atmosphere
UVA – UVA activates melanin already present in the upper skin cells but the tan is lost quickly. Penetrates deeper into the skin, damages the dermis (middle skin layer), accelerates aging, causes wrinkles, increases oxidation and suppresses cutaneous immune function.
UVB – UVB stimulates the production of new melanin, and a longer lasting tan. Also stimulates a thicker epidermis. Absorbs by the epidermis (top skin layer).
It’s not just the sun, it’s also the ozone.
We all know that the ozone layer is thinning and the thinner ozone has allowed more UVB rays to come through the atmosphere.
Sun protection
Sun protection has been covered in various interviews with dermatologists on this blog but the point to emphasize is that for babies, it is very important to avoid the sun and practice sun protection because:
Thinner skin
Less melanin-producing skin cells
Larger surface area to body ratio
Increased absorption of chemicals and vulnerability to irritants in sunscreen products make sun avoidance a wiser choice
Lips and eyes are also affected by UV rays, thus wearing a wide-brimmed hat and sunglasses are also part of sun protection.
It is recommended to use physical blockers/ inorganic filters such as zinc oxide (more UVA protection) and titanium dioxide (more UVB protection). As opposed to chemical absorbers, physical blockers do not penetrate more than two layers of stratum corneum and therefore less likely to induce skin irritation and sensitization. Moreover, infants tend to rub their eyes and may inadvertently rub the sunscreen into their eyes and won’t be able to ‘get rid’ of it as (i) their tear secretions and (ii) their blinking mechanism are not fully developed.
A note on SPF
SPF is the measure of ratio of UV rays before sunburn and SPF 30 means that the skin is able to take 30 times higher dose of UV rays before sunburn. The amount of sunscreen to apply is 2mg/cm2. Broad spectrum refers to additional UVA absorbers (avobenzone and octocrylene) being added to the physical blockers.
For these 8 weeks, we’re going ‘intensive’ into skin facts. Many articles have shared about adult skin facts, but in #SkinishMom style, we’re ‘digging’ deeper into children’s skin and eczema skin. (Note: all skin facts have published data for children and eczema skin)
Some ‘Skin Investigation’ may turn up with unexpected facts!
Skin Fact #1 Skin is (NOT!) the largest organ in the body
Oops, doesn’t everyone say that skin is the largest organ? That’s why some ‘skin’ investigation is required for ‘skin journalism’. Located a letter to editor in the Journal of Investigative Dermatology that skin is not the largest organ in the body. The skin can be considered the largest BY WEIGHT for ‘medium-sized’ organs, excluding musculoskeletal system.
Skin (epidermis and dermis) weights 3.86kg, about 5.5% of a 70kg man
Subcutaneous tissue (layer of fats under the dermis layer) is not consider skin
Skin is not the largest organ by surface area, about 1.7 sqm but lung airway is 70sqm, and gastrointestinal tract is about 30-40sqm (note in the letter to editor, it’s stated as about football field, but in a paper that subsequently published in 2014 Scandinavian Journal of Gastroenterology, scientists measured the inner surface of gastrointestinal tract of a healthy average man; previous estimates of the gastrointestinal tract were made post-mortem where the tract has relaxed to a much longer length! ‘Interesting!’)
Skin Fact #2 Adult skin sheds about 17kg to 52kg over a lifetime
From research and as explained by Dr Claudia Aguirre on Quora (Dr Claudia is a featured guest of this blog), humans shed their entire outer layer of skin every 2-4 weeks at the rate of 0.001 — 0.003 ounces of skin flakes every hour. This worked out mathematically to be 17kg to 52kg (or 37 to 115 pounds) for someone who live up to over 70 years old (I’d suppose that the 0.001 to 0.003 ounces is for an average adult, thus strictly speaking, you can’t simply multiply by 70 due to (possibly?) less skin shed for a child (by weight, but given larger surface area to volume ratio, a child may shed ‘more’ skin).
Eczema skin – Eczema skin, characterized by dry skin, shed more skin (and add the scratching!). The outer skin layer (epidermis) has four layers of keratinocytes (skin cells). The keratinocytes at the basal layer continually grow and move upwards to the stratum corneum, changing from plump cells to dead, flattened cells that are shed. This takes about 28 days. I couldn’t find research on how much skin an eczema sufferer shed, but there’re two ‘opposite’ skin conditions worth mentioning:
Exfoliative Dermatitis – characterized by extensive red skin, followed by skin shedding (similar to life-threatening conditions covered in this blog: Stevens Johnson Syndrome and Erythroderma); the skin shedding is so extensive in these conditions that it affect the normal functioning of the body, in particular temperature regulation and moisture retention, requiring care in hospital.
Psoriasis – this condition is marked by only taking 3 to 4 days to mature and does not shed but the skin cells pile up on the skin surface, forming plaques and lesions.
Many eczema sufferers reported seeing massive skin shed on the bed and floor but I wonder why the skin cells shed appear so visible (as opposed to normal skin). Found an explanation that the cells on dry skin may stick together, thickening the stratum corneum and when they are shed, it is shed as visible sheets, aka scales.
Skin Fact #3 Dead skin cells comprised an UNKNOWN part of our dust at home
This is another ‘fact’ that could turn out to be a myth – most of the sites state that our dead skin made up anywhere from 50% to 90% of our dust at home. In a study by Layton and Beamer whose study was to find out how much of contaminated soil and outdoor pollutants would get into home dust, it was estimated that about 60% would come from outdoors. Dust is very complicated, with different home, season, surrounding and the type of dust in the air and on the floor being different. It cannot be simplified to state as most of the dust are dead skin cells.
What we have to know is dead skin cells are food for house dust mites and they literally sleep with us, in our bedsheet, pillow, pillow case and mattress. Read the following posts to understand more about dust mites:
I shared in this post (and the comments) that moisturizing has been studied to have a protective effect over eczema. Similarly, Dr Cheryl Lee MD shared in the Skin pH interview series that moisturizing from 3 weeks of age has been shown by Simpson et. al., to be a safe and effective time to start moisturizing the skin of a newborn who is at high risk of developing atopic dermatitis.
The question is it is not always clear whether the baby has high eczema risk. If a baby can get a non-invasive test and parents are then alerted to moisturize their baby early, many babies can have a chance of not suffering from eczema. More about this test:
Title of study: Skin barrier dysfunction measured by transepidermal water loss (TEWL) at 2 days and 2 months predates and predicts atopic dermatitis at 1 year.
Method: Measure water evaporation in the skin of 1,903 newborn babies in Cork University Hospital, and followed them up until 12 months of age.
How: Small probe placed on the child’s arm to measure the level of water evaporation at day 2 and 2-month & 6-month old.
Results: A higher water loss at 2-day and 2 month strongly predict eczema at 12 months.
This study is only published in 22 Jan 2015, I’m interested to see if this test will be adopted by pediatricians. Maybe you can bring this up to your doctor to see if such a test can be arranged for your newborn! If you did talk to your doctor, let me know the response so that other parents can benefit from it.
