Good question. Since the hyaluronic acid (HA) filler is reversible with hyaluronidase, that maybe a safer option. Our skin and joints and other parts of our body makes natural hyaluronic acid gel so it is less likely to cause an immune response. When there is the rare allergic response, it may be to the bacterial proteins that maybe present in very tiny quantities from the manufacturing process. Most of it is washed out, but some may be present. When switching brands, the same allergy may not be present since the manufacturing process is different, so the allergy is unlikely to the hyaluronic acid gel itself. Allergy tests are not required before hand prior to treatment.
