Background: Chemically modified allergen extracts, known as allergoids, are commonly
used for treating allergic patients. In general terms, the concept of allergoids implies allergen extracts
with a reduction of their allergenicity maintaining their immunogenicity. Different methods to obtain
allergoids have been developed in the past years, opening attractive lines of research.
Objective: To review the different approaches to allergoid development as well as their characterization,
mechanism of action and efficacy and safety issues.
Methods: A revision and analysis of the different types of allergoids has been performed, with special
attention to patents submitted and granted in the last years. Additionally, updated information about the
mechanism of action and clinical evidence and safety of allergoids has been discussed.
Results: Principally, allergoids are obtained by the polymerization of native allergen extracts with aldehydes,
including formaldehyde or glutaraldehyde. However, recent patents and publications about different
chemical modifications have been presented, as well as about the use of new adjuvants with allergoids.
Regarding the characterization, allergoids require more sophisticated analytical methods than
native extracts, as a consequence of their properties and characteristics.
Conclusion: In the last years, the partial understanding of the mechanism of action and the generation
of clinical evidence of different types of allergoids, linked to their excellent safety profile and their
convenience for a quick build up phase, have made of allergoids an excellent product for allergy treatment.