Basics of Extract Manufacture < Extractopedia

Source Material Collection

The manufacture of an allergenic extract begins with the identification and procurement of a natural source material. 1 Source material collection is a process that results in a relatively pure sample of allergenic substances (e.g., pollen, dander/epithelium, fungal cultures, whole insects, foods, etc.). A successful collection of allergenic material can depend on a number of factors: The distribution of a desired species, reliability of collectors, and seasonal climate fluctuations are all issues that can affect source material availability and consistency. Likewise, these factors can also impact the downstream availability and consistency of the final extract product.


Extraction is the process by which water soluble proteins and other bioactive molecules are removed from the allergenic source material and held in solution. The extraction process utilizes a series of quality- controlled methods to help avoid contamination and promote product stability.3. The final composition and lot-to-lot consistency of an extract may be affected if these extraction procedures are not carefully followed.


Characterization involves any number of analytical methods that can be used to better evaluate an allergenic extract. In general, most manufacturers employ a standard set of methods to assess the identity, sterility, potency, and stability of an extract. ALK has developed additional assays that allow us to quantify the major allergen content for certain extracts. Major allergens are allergenic proteins to which the majority of patients are sensitized to. While, in theory, patients can become sensitized to any protein, in practice, most patients develop sensitivity to a select number of these proteins. These assays offer an additional approach to determining an extract’s composition, consistency, and stability. This is especially true for extracts that currently lack FDA methods for standardized but have validated major allergen measures, such as Birch.


The FDA has defined a biologic potency value for a limited number of extracts that are commonly used for the diagnosis and treatment of allergy. 2. There are currently 17 standardized products including: Cat, Dust Mites (D. farinae & D. pteronyssinus), Hymenoptera Venom, Short Ragweed, and 8 Grasses.

The standardization process requires that all manufacturers perform additional testing with an FDA-approved laboratory method in order to verify that an extract meets the defined standard of potency. The primary goal of standardization is to ensure a supply of allergenic extracts that exhibit consistent potency, which should lead to greater patient safety.

The recommended dosing guidelines for U.S. standardized products are extrapolated primarily from the major allergen values determined to be efficacious in European clinical trials.


  1. 1. COR-US-18-000017-009. Major Allergens and Allergenic Extracts. ALK Technical Memo, November 2018.
  3. 2. Morrow, KS, & Slater, JE. Regulatory aspects of allergen vaccines in the US. Clin Rev Allergy Immunol. 2001 Oct;21(2-3):141-52.
  5. 3. Plunkett, G. 2008. Stability of allergen extracts used in skin testing and immunotherapy. Current Opinion in Otolaryngology & Head and Neck Surgery 2008, 16:285-291.