Products
Gels are commercially available as pharmaceuticals, medical devices and cosmetics.
Structure and properties
Gels consist of gelled liquids. They are prepared with suitable swelling agents (gelling agents). These include, for example, celluloses (e.g., hydroxypropyl cellulose), starches, carbomers, gelatin, xanthan gum, bentonite, agar, tragacanth, carrageenan, and pectin. The pharmacopoeia distinguishes between hydrophilic and lipophilic gels. They may be translucent or opaque. Other possible ingredients include water, propylene glycol, antioxidants, lipids (for lipogels), flavorings, sweeteners and preservatives.
Production of gels
A common problem when making gels is the formation of lumps. Listed below are some tips to prevent this:
- Make gel under vigorous stirring with a mechanical stirrer.
- Slowly sift the powder into the liquid.
- Note different solubility in cold and hot water.
- Rub powder with an alcohol or ketone. Typical examples are ethanol and propylene glycol.
Effects
Gels have a short-term hydrating effect and cooling effect due to the evaporation of water. They have little skin care properties and are rather drying.
Fields of application
For local or systemic administration of active ingredients. Gels are used for the treatment of insect bites, sunburn, in sports injuries, rheumatic complaints, muscle and joint pain, and calf cramps, among others. Sterile hydrogels are used in wound care to keep wounds moist, e.g. in dry necroses or simple wounds in the granulation and epithelization phase. Either the gel alone or the gel completed in a dressing is placed on the wound.
Disadvantages
Gels are less skin-caring than creams and ointments. Because of their high water content, they are susceptible to microbial contamination. They can dry out, and some must be broken down within a certain period of time after opening. Incorrect manufacture can result in lumps.
