Local reactions are by far the most common and, according to clinical studies show a statistical frequency ranging from 0.05 to 0.69% 3. Signs include significant edema, erythema, pain and itching. Urticaria and angioedema have been reported in less than 0.1% of cases 16. Anaphylaxis occurred with hyaluronidase when high dosages were used by IV route (please refer to the Expert group on esthetic complications, guideline for anaphylaxis).
Hypersensitivity reactions of type I (IgE mediated) and type IV (T-cell mediated) have also occurred following treatment with hyaluronidase. After the use of hyaluronidase the patient must remain for a period of observation in a clinical setting. In rare cases the administration of hyaluronidase may cause anaphylaxis (a severe allergic reaction) requiring immediate medical intervention. Symptoms of a severe allergic reaction can include: lack of breath, wheezing, cough, difficulty in swallowing, swelling of the tongue, eyelids and lips, hoarseness, stomach ache, nausea and diarrhea. Hyaluronidase has an off-label indication for esthetic medicine and, except in cases of emergencies for vascular impairment, patients must undergo a skin patch test at least 20 minutes before treatment. The test is performed through an injection of hyaluronidase in the subcutaneous tissue of the forearm, and observing possible reaction signs (ie. wheal). Should the patch test yield a positive result, treatment with hyaluronidase must be avoided. Erythema or reddening with moderate vasodilation may also be observed.