all you need to know about your skin
Skin is the exterior organ that covers the human body, as well as the body of other vertebrates. It is the first layer that comes in contact with exterior factors, helping to protect us from external dangers. Because of its dense network of sensitive nerve endings, skin acts as a sensory organ as well. It also helps regulate our body temperature and is capable of activating vitamin D after UV exposure.
Skin thickness varies greatly across the human body; it is thinnest around the eyes, where wrinkles tend to first appear, while the heels and palms are covered with notably denser skin.
It was long believed that skin was an impermeable barrier. Although it is true that skin does not allow bigger compounds to penetrate it, such belief was revised after the skin was found to be permeable to many substances, including most skincare products. This permeability can allow the introduction of chemicals (such as coal tar and phthalates) into the human body. The skin can also be a targeted port of entry for numerous drugs, whose active ingredients (such as hormones or nitroglycerin) are delivered to the circulatory system, via the skin, through medicated creams, ointments, or patches.
The skin is divided into three layers:
- epidermis (the most exterior)
- dermis
- hypodermis
Keratinocytes, which make up to 95 percent of the epidermis cells, migrate from the stratum germinativum up toward the stratum corneum. As this migration occurs, keratinocytes become highly organized, secrete keratin (the main protein of the epidermis) and lipids, lose their nuclei (become dead cells), and are then shed through the natural process of desquamation, or peeling.
The epidermis and dermis meet at the level of the basement membrane, which is a thin layer of fibers. The dermis is a dense network of connective tissues, blood and lymphatic vessels, nerve endings, hair follicles, and sweat and sebaceous glands. The hypodermis is a connective tissue that ties the dermis to the muscles, bones, vessels, and nerves. It hosts adipose cells (fat cells), collagen cells, and sweat glands. A reduction in the mass of this section of the skin contributes to skin sagging.
Moisturizers can significantly hydrate only the upper layers of the epidermis. The actual nutrition of deeper epidermis cells happens by diffusion from a network of capillaries found in the underlying dermis, which is why proper hydration and balanced nutrition are strong contributors to better-looking skin.
Unlike moisturizers, which act at the level of the upper layers of the epidermis, pharmaceutical topical drugs are formulated to achieve deeper skin penetration. The active ingredient is delivered to deeper layers, where it can exert a local or systemic effect. Examples of such drugs include the nitroglycerin patch, anti-inflammatory creams, and medicated gels.
Skincare products can also be formulated with a deeper penetration objective; for example, a product designed to improve collagen production might need to incorporate penetration enhancers into the formula to maximize the delivery of its collagen-promoting ingredients. Such formulas can be micro-emulsions, whose bipolar droplet size encourages passage through skin layers; or they can contain powerful solvents that will transport other ingredients to lower skin levels. Such formulations may not totally comply with the FDA definition of cosmetics, which are not supposed to affect bodily functions; but they remain popular because of the promised results.
Skin Types
There are five basic skin types: normal, oily, dry, combination, and sensitive.
Normal skin has an adequate balance of sebum and moisture, which contributes to its smooth and even surface. Normal skin does not feel greasy or dry, has good elasticity, and tolerates most environmental challenges. It needs only basic care and rarely requires special treatment regimens.
Oily skin has mild to moderately overactive sebaceous glands, which lead to an excess in sebum production. Skin feels greasy to the touch, especially on the nose and forehead areas, and requires daily or twice daily cleaning to remove accumulated oils. Excess sebum can gather both dust and bacteria, which is why oily skin is prone to black and whiteheads, as well as blemishes and acne. Astringents are widely used on oily skin since they decrease the size of pores and help reduce sebum production. Antibacterial agents are also useful in controlling bacterial proliferation. Nevertheless, excess cleaning is not recommended because it is thought to further stimulate sebaceous glands and contribute to maximized sebum production and a significant rebound effect, especially when care is withheld.
Dry skin lacks both oily secretions and moisture. Because of the insufficient quantity of sebum produced by the sebaceous glands, the skin coating is unable to adequately prevent moisture loss and maintain a well-hydrated skin. Dry skin tends to wrinkle more easily and can become chapped in challenging weather conditions such as extreme cold. It is very important to apply moisturizers and creams specially formulated for dry skin, which tolerates higher percentages of oils, or even butters.
Combination skin, a very common type of skin, is a mixture of both dry and oily skin, in which oily skin covers the forehead, nose, and chin (the T-zone), and dry skin covers the cheeks and the area around the eyes. Theoretically, each zone should be treated according to its type, unless the skincare regimen is specifically designed for combination skin.
Sensitive skin often has a very fine texture and poor tolerance to many elements, which can turn out to be irritating and sensitizing. Such elements could be soap, synthetic fragrances, artificial preservatives, dyes, and even temperature changes and aggressive weather. Simple, fragrance-free, hypoallergenic, and purely natural skincare products are usually the best regimens for sensitive skin types.
Skin Patch Test
Because skin reactions can be unpredictable, testing the skin tolerance to a new product is essential to detect potential allergies. This is usually done prior to using any product for the first time, whether it is store-bought or homemade. It is very easy to test your skin for a reaction prior to normal application by applying a little of the product on a small and discreet area; it takes only twenty-four hours to get results. Homemade formulations are usually very well tolerated; most reactions tend to occur when acidic compounds (such as lemon juice or yogurt) are included. The formulas in this book are designed to include well-tolerated amounts of such ingredients, so that they can be effective while reducing the risk of sensitivity.
People with sensitive skin and people who tend to break out easily should be more cautious when trying new products. Still, because every person skin is unique, and because tolerability varies greatly between individuals, a skin patch test is highly advisable, no matter the skin type, to avoid potential skin reactions.
Apply a pea-size amount of the product to the inside of your elbow. Cover with gauze and wait for twenty-four hours before removing it. Covering the test area with gauze prevents the product from being rubbed off. Avoid getting the bandage wet during testing time. Remove the patch immediately if you notice any signs of allergy such as redness, swelling, rash, itching, or tingling or burning sensations. If this happens, rinse the affected skin area with plenty of warm water, without scrubbing to avoid further irritation, and discontinue the product use. Contact a dermatologist if your symptoms do not improve. Otherwise, remove the gauze after twenty-four hours and examine the area for any signs of allergy. No reaction means that it should be okay to use the product. Discontinue use if a reaction occurs upon secondary applications.
Skin Nutrients
Multiple components come together to form and maintain skin. Water, proteins, fats, minerals, vitamins, and other nutrients are essential for maintaining the balance of the skin and mucosal tissues. Skin is capable of renewing itself every twenty-seven days, on average. Older cells are lost through shedding, and newly differentiated ones replace them. Diet and skincare have a great effect on skin cells since the skin needs specific nutrients that can be provided through diet, topically or both. Studies have shown that diets rich in vegetables, fruits, fish, and olive oil contribute to better-looking skin. It is also established that adequate hydration can lead to better skin moisture levels.
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