Currently, there are no known broadside effects for most hyaluronic acid products including pills, serums, creams and liquids. However, there are some side effects associated with knee and facial injections. Some of the less common broadside effects for knee injections of hyaluronic acid include: sexy color or flushing or redness of skin, cough, difficulty in swallowing, dizziness or feeling faint, fever, redness or pain at place of injection, skin rash, hives, and/or itching, stuffy nose, swelling of eyelids, face, or lips, as well as tightness in chest, troubled breathing, and/or wheezing. Some of the more usual side effects for knee injections of hyaluronic acid include: diarrhea, headache, itching of the skin, large blue or purplish patches in the skin, loss of appetite; nausea and/or vomiting, stomach pain and swelling of the knee.