Purified vs. nonpurified venom immunotherapy

Although highly effective, venom immunotherapy (VIT) may be responsible for local and systemic allergic reactions. There is a good theoretical basis for believing that purified aqueous and purified aluminium hydroxide adsorbed (so-called depot) extracts, commercially available in Europe, have the potential to reduce the incidence of VIT's side effects. The aim of this article is to review the literature on safety and effectiveness of purified preparations as well as compare them with nonpurified extracts.

Old and new noncomparative studies reveal good tolerance of purified aqueous and purified depot extracts. In comparative trials purified extracts appear to be better tolerated than nonpurified extracts, whereas depot extracts seem to be safer than the corresponding purified aqueous preparation, especially in the prevention of severe large local reactions. The efficacy of purified aqueous and depot extracts is supported by studies using both sting challenge and in-field stings and is comparable to that of nonpurified preparations.

The theoretical basis of the safer profile of purified extracts is supported by a number of clinical studies, making the use of purified depot preparations preferable for conventional treatment also by specialists with less experience in managing VIT. In specialized centres purified aqueous extracts may be preferred for faster build-up protocols. However, further prospective controlled studies are needed in order to evaluate the ability of purified extracts to reduce the frequency of severe systemic reactions over the corresponding nonpurified preparation.