Lotions are applied to external skin with bare hands, a brush, a clean cloth, cotton wool, or gauze. While lotion may be used as a medicine delivery system, many lotions, especially hand lotions and body lotions are meant instead to simply smooth, moisturize and soften the skin. These may be used in anti-aging lotions, which can also be classified as a cosmetic in many cases, and may contain fragrances. The Food and Drug Administration voiced concern about lotions not classified as drugs that advertise anti-aging or anti-wrinkle properties.
Dermatologists can prescribe lotions to treat or prevent skin diseases. It is not unusual for the same drug ingredient to be formulated into a lotion, cream and ointment. Creams are the most convenient of the three but are inappropriate for application to regions of hairy skin such as the scalp, while a lotion is less viscous and may be readily applied to these areas (many medicated shampoos are in fact lotions). Historically, lotions also had an advantage in that they may be spread thinly compared to a cream or ointment and may economically cover a large area of skin, but product research has steadily eroded this distinction. Non-comedogenic lotions are recommended for use on acne prone skin.
Lotions can be used for the delivery to the skin of medications such as:
- Anti-acne agents
- Soothing, smoothing, moisturizing or protective agents (such as calamine)
Since health care workers must wash their hands frequently to prevent disease transmission, hospital grade lotion is recommended to prevent skin dermatitis caused by frequent exposure to cleaning agents in the soap. A 2006 study found that application of hospital grade lotion after hand washing significantly reduced skin roughness and dryness.
Most lotions are oil-in-water emulsions using a substance such as cetearyl alcohol to keep the emulsion together, but water-in-oil lotions are also formulated. The key components of a skin care lotion, cream or gel emulsion (that is mixtures of oil and water) are the aqueous and oily phases, an emulgent to prevent separation of these two phases, and, if used, the drug substance or substances. A wide variety of other ingredients such as fragrances, glycerol, petroleum jelly, dyes, preservatives, proteins and stabilizing agents are commonly added to lotions.
Since thickness and consistency are key factors in lotions and creams, it is important to understand the manufacturing process that determines viscosity.
Manufacturing lotions and creams can be completed in two cycles:
- Emollients and lubricants are dispersed in oil with blending and thickening agents.
- Perfume, color and preservatives are dispersed in the water cycle. Active ingredients are broken up in both cycles depending on the raw materials involved and the desired properties of the lotion or cream.
A typical oil-in-water manufacturing process might go like this:
- Step 1: Add flake/powder ingredients to the oil being used to prepare the oil phase.
- Step 2: Disperse active ingredients.
- Step 3: Prepare the water phase containing emulsifiers and stabilizers.
- Step 4: Mix the oil and water to form an emulsion. (Note: This is aided by heating to between 110-185 F (45-85 C) depending on the formulation and viscosity desired.)
- Step 5: Continue mixing until the end product is completed
Careful note should be taken in choosing the right mixing equipment for lotion manufacturing to avoid agglomerates and long processing times. It can make all the difference in manufacturing time and costs. Conventional agitators can present a number of problems including agglomerates and longer processing times. On the other hand, high shear in-line mixers can produce quality lotions and creams without many of the complications encountered with conventional mixers. Sonolation is also a process that is growing in popularity.
Potential health risks
Depending on their composition, lotions can be comedogenic, meaning that they can result in the increased formation of comedones. Sufferers of acne, or those who are predisposed to forming comedones, should look for formulations that are designed to be noncomedogenic.
All topical products, including lotions, can result in the percutaneous absorption of their contents. Though this has limited use as a route of drug administration, it more commonly results in unintended, and often undesirable, consequences. For example, medicated lotions such as Diprolene are often used with the intention of exerting only local effects, but absorption of the drug through the skin can occur to a small degree, resulting in systemic side effects such as hyperglycemia and glycosuria. Absorption is increased when lotions are applied and then covered with an occlusive layer, when they are applied to large areas of the body, or when they are applied to damaged or broken skin.
There is currently no regulation over use of the term "hypoallergenic", and even pediatric skin products with the label were found to still contain allergens. Those with eczema are especially vulnerable to an allergic reaction with lotion, as their compromised skin barrier allows preservatives to bind with and activate immune cells.
The American Academy of Allergy, Asthma, and Immunology warns that natural lotion containing ingredients commonly found in food (such as goats milk, cow's milk, coconut milk, or oil) may introduce new allergies, and an allergic reaction when those foods are later consumed.
Impact on the body's natural process
Lotions are mainly intended to help the skin, but can also harm your skin. Christina Marino, who practices at Johns Hopkins Community Physicians, has conducted much research on this aspect. Moisturizers contain ingredients that are either occlusive or humectant. Occlusive agents are used to help block the loss of water from the skin. Humectant agents are used to attract water to the skin. Significant water exposure to the skin can cause the loss of soluble natural factors. Persistent moisturization to the skin from exposure to water may contribute to an allergic reaction or irritant contact dermatitis, and can result in penetration of foreign objects. Changes in the skin's normal ecological environment, in or on the skin, can support the overgrowth of pathological organisms. Lotions contain 65-85% of water. Water acts as an agent to disperse the active and inactive ingredients in the lotion. A high water content also serves as a way for the absorption of some components and evaporation of the moisturizer. Water acts as a temporary hydration agent.
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