Absorption (skin)

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Skin ingestion is the route through which substances can enter the body through the skin. Along with inhalation, consumption and injection, skin absorption is the route of exposure to toxic substances and drug delivery routes. Absorption of the substance through the skin depends on a number of factors, the most important is the concentration, contact duration, drug solubility, and the physical condition of the skin and exposed body parts.

Skin absorption (percutaneous, skin) is the transport of chemicals from the outer surface of the skin both into the skin and into the circulation. Skin absorption is related to the level of exposure and the possible effects of a substance that can enter the body through the skin. Human skin is in contact with many agents intentionally and unintentionally. Skin absorption may occur from skin exposure in the workplace, the environment, or consumers against chemicals, cosmetics, or pharmaceutical products. Some chemicals can be absorbed in sufficient quantities to cause adverse systemic effects. Skin disease (dermatitis) is considered one of the most common occupational diseases. To assess whether a chemical can be a good risk of causing dermatitis or other systemic effects and how that risk can be reduced, one should know the extent to which it is absorbed, so skin exposure is a key aspect of human health risk assessment..

Video Absorption (skin)

Factors affecting absorption

Along with inhalation, consumption and injection, skin absorption is the route of exposure to bioactive substances including drugs. The absorption of a substance through the skin depends on a number of factors:

• Concentration
• Molecular Weight of molecules
• Contact duration
• Solubility of the drug
• The physical condition of skin
• Exposed body parts include the amount of hair on the skin.

In general the rate of chemical absorption through the skin follows the following scheme from fastest to slowest: scrotum & gt; Forehead & gt; Armpit> = Scalp & gt; Return = Abdomen & gt; Palm = below the surface of the foot.

Maps Absorption (skin)

Structure affects absorption

To be absorbed through the skin, chemicals must pass through the epidermis, glands, or hair follicles. Sweat glands and hair follicles form about 0.1 to 1.0 percent of the total surface of the skin. Although small amounts of chemicals can enter the body rapidly through the hair glands or follicles, they are mainly absorbed through the epidermis. Chemicals must pass through seven layers of epidermal cells before entering the dermis where they can enter the bloodstream or lymph and circulate to other areas of the body. Toxins and toxins can move through layers with passive diffusion. The stratum corneum is the outermost layer of the epidermis and a rate-limiting inhibitor in agent absorption. Thus, how fast something passes through this thicker outer layer determines the overall absorption. Stratum corneum consists mainly of lipophilic cholesterol, cholesterol ester and ceramide. Thus, lipid-soluble chemicals make it through the coating and into the circulation more quickly, but almost all molecules penetrate to a minimal level. The absorption of urban water chemicals and dental products such as VOC, TTHM, fluoride and disinfectants is a major exposure to environmental health hazards.

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Conditions affecting skin absorption

Agents that injure the stratum corneum, such as strong acids, are absorbed more rapidly than chemicals that do not. Skin damage from burns, abrasions, injuries and skin diseases also increases absorption. Thus populations with skin damage may be more susceptible to the adverse effects of agents being absorbed through the skin. Certain solvents such as dimethyl sulfoxide (DMSO) act as carriers and are often used to transport drugs through the skin. DMSO increases stratum corneum permeability. Surfactants such as sodium lauryl-sulphate increase skin penetration of water-soluble substances, possibly by increasing water skin permeability.

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Medical use of skin absorption

Dermal applications of drugs or chemicals allow treatment to be localized, unlike ingestion or injection. Some drugs seem to be more effective (or more efficient) using dermal administration routes. Some ingested drugs are metabolized heavily by the liver and may be inactive, but using dermal applications through this metabolic step allows more parent compounds to enter the peripheral circulation. If the drug is well absorbed through the skin it can be used as a systemic treatment device. Dermal dermal forms include: liniments, braces, lotions, ointments, creams, dust powders, aerosols, and transdermal patches. Specially designed fillings are currently used to deliver fentanyl, nicotine and other compounds. Slower skin absorption than oral or injectable allows the patch to provide medication for 1 to 7 days. For example nitroglycerin given transdermally may provide hours of protection against angina while the duration of sublingual effects may be only a few minutes.

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Skin absorption measurements

The amount of chemicals absorbed through the skin can be measured directly or indirectly. Studies have shown there are species differences in the absorption of different chemicals. Measurements in rats, rabbits or pigs may or may not reflect human absorption. Finding the rate at which the agent penetrates the skin is important to assess the risk of exposure.

Live measurements

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Chemicals can be directly applied to the skin followed by measurement of blood and urine at a specific point in time after application to assess the amount of chemicals that enter the body. Concentrations in blood or urine at a given point in time can be described to show and areas under the curve and the rate and duration of absorption and distribution to provide a systemic absorption measure. This can be done on animals or humans with dry chemical powders or chemicals in solution. Mice are usually used for this experiment. The skin area is shaved before chemicals are applied. Often the area of ​​chemical applications is covered to prevent consumption or scrub the test material. Blood and urine samples were taken at certain time intervals after application (0.5, 1, 2, 4, 10, and 24 hours) and in some protocols at the selected end-time the animal may sample necropsies and tissues can also be evaluated for chemical presence test. In some test protocols many animals can be tested and necropsy can occur at certain intervals after exposure. Biomonitoring, such as taking urine samples at intervals, from workers exposed to chemicals may provide some information but it is difficult to differentiate skin from inhalation exposure using this method.

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The nature of the stratum corneum permeability, for the most part, remains unchanged after removal from the body. Carefully removed skin from animals can also be used to see how far local penetration is by putting it indoors and applying chemicals on one side and then measuring the amount of chemicals entering the liquid on the other. One example of this ex vivo technique is the isolated porcine perfusion cover. This method was first described in 1986 as a humane alternative to animal testing in vivo.

In vitro

Techniques such as static diffusion cells (Franz cells) and flow-through diffusion cells (Bronaugh cells) have also been used. The Franz Cell apparatus consists of two chambers separated by animal or human skin membranes. Human skin is preferred but because ethical and other considerations are not always available. Human skin often comes from autopsies or plastic surgery. The test product is applied to the membrane through the upper chamber. The lower space contains the liquid from which the sample is taken periodically for analysis to determine the active number that has penetrated the membrane at the designated time point.

Bronaugh cells are similar to the Franz cells but use a system of flow-through beneath the membrane layer and the liquid samples below are taken continuously rather than at the designated time points. Bronaugh cells have been replaced by inline cells by some manufacturers.

Indirect measurements

Sometimes it is impossible for a humane reason to use a drug on the skin and measure its absorption. Sarin, a nerve gas, can be absorbed through whole and deadly skin at low concentrations. So if one needs to assess Sarin exposure risk one must take skin absorption and other routes into account but one can not ethically test Sarin on human subjects; thus the way the risk modeling of the agent skin exposure has been found.

If exposure and absorption of the skin is considered to indicate the risk of various methods to reduce the absorption can be done.

• The chemicals label may be adjusted to require the use of gloves or protective clothing.
• Warnings are immediately washed if chemicals in contact with skin can be made.
• Close swimming pool or lake to swimmer.
• Limit the exposure time of chemicals, ie workers can only work with certain chemicals for a certain period of time per day.

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See also

• Absorption (chemistry)
• Absorption (pharmacokinetics)
• Dermal patch
• Epidermis (skin)
• Exposure assessment
• Exposure to poison
• Topical treatment

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References

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External links

• Exposure & amp; Skin Effects, Centers for Disease Control and Prevention
• EDETOX Database
• WHO, Environmental Health Criteria 235, Dermal Absorption
• Standard Operation Procedure of EPA 2012 (SOP) for Assessment of Housing Exposure
• Franz cell description
• [1]

Source of the article : Wikipedia