Mixing Concerns: Cross-Reactivity & Proteolytic Enzymes < Extractopedia

Use of Allergen Extracts  >  Mixing Allergens  >  Mixing Concerns: Cross-Reactivity & Proteolytic Enzymes

Mixing Concerns: Cross-Reactivity & Proteolytic Enzymes

Some patients who present as polyallergic may require treatment with a mixture of different clinically relevant allergens. In the United States, it is standard practice to mix multiple allergens into a single treatment vial. This is generally not a problem; however, there are two principles that should be considered:

Cross-reactivity Extracts

Certain allergens should not be combined into the same treatment vial due to cross-reactivity. Cross-reactive allergens from different species of grass pollen or house dust mite, for example, share many of the same allergenic protein structures. Adding more than one cross-reactive species can potentially lead to a multiplication of dose, which might cause adverse reactions for sensitive patients. Thus, cross-reactivity should be considered to obtain optimal therapeutic dosage of each component by limiting the number of allergens in a treatment vial. In these cases, a single representative species, or a stock mix, might be the most appropriate for treatment.

For further information, please see the section on the Importance of Cross-Reactivity.

Proteolytic Extracts:

Research studies suggest that some allergen extracts, such as pollens, are susceptible to degradation when mixed with extracts that show high proteolytic activity, such as molds or insects. 1, 2. Proteases are enzymes that catalyze the breakdown of proteins by cleaving the peptide bonds within the protein. Their presence in allergen mixtures can lead to a significant reduction in potency of the allergen extracts, and therefore, a reduction in potential efficacy of these extracts. Pollen and epidermal extracts can be mixed since they do not demonstrate proteolytic activity.

It is recommended that allergens with high proteolytic activity be mixed separately. Mold and insect extracts can be mixed with each other but should not be mixed with pollen or epidermal extracts. Dust mite extracts have shown stability when mixed with either mold/insect or pollen/epidermal extracts. 3.

Hymenoptera venom extracts should be kept separate from other extracts since they are formulated for independent use.

Group A

(High proteolytic activity)

Should be mixed separately

Group B

(Little or no proteolytic activity)

Should not be mixed with allergens in Group A)

Group C

Can be mixed with either Group A or Group B


Insects (Cockroach, Fire, Ant)

Grass Pollen

Tree Pollen

Weed Pollen

Dander/ Epithelial

House Dust mite extracts

Note: Hymenoptera venom extracts should be used separate from the other extracts.


  1. 1. Esch RE. Allergen immunotherapy: what can and cannot be mixed? J Allergy. Clin Immunol 2008;122:659-60, IV.

  2. 2. Grier TJ, LeFevre DM, Duncan EA, Esch RE. Stability of standardized grass, dust mite, cat, and short ragweed allergens after mixing with mold or cockroach extracts. Ann Allergy Asthma Immunol 2007;99:151-60, LB.

  3. 3. Nelson HS, Ikle D, Buchmeier A. Studies of allergen extract stability: the effects of dilution and mixing. J Allergy Clin Immunol 1996;98:382-8, LB.