Collagen injections work to temporarily or permanently smooth and plump skin by promoting collagen growth under the surface, defines HowStuffWorks. The common cosmetic procedure is often used to treat facial wrinkles between the mouth and nose, lessen the appearance of scarring, fill hollow cheeks and repair facial imperfections.
Collagen injections are available in bovine, human and synthetic form, states HowStuffWorks. Collagen fillers made from cow skin are typically inexpensive, but involve a greater risk of allergic reaction; the use of human collagen rarely results in such reactions, but may cost significantly more. Synthetic collagen is created by adding preservative chemicals to human and cow collagen, enabling them to remain in the body for longer periods.
Redness and puffiness around the injection site and slight bruising are common side effects of collagen injections, according to HowStuffWorks. Substances such as green tea, alcohol, St. John’s wort and aspirin should be avoided, as they are known to increase this bruising. Doctors often require patients subject to non-biodegradable fillers to complete an allergy test prior to treatment, where a small amount of a substance is injected into the skin. In screening for allergies, the injection site may then be monitored for allergic reactions for up to four weeks, report HowStuffWorks contributors.