Infectious disease vaccine potency is affected by antigen adjuvant adsorption. WHO and EMA guidelines recommend limits and experimental monitoring of adsorption in vaccines and allergy immunotherapies. Adsorbed allergoids and MPL® in MATA-MPL allergy immunotherapy formulations effectively treat IgE mitigated allergy. Understanding vaccine antigen adjuvant adsorption allows optimisation of potency and should be seen as good practice; however current understanding is seldom applied to allergy immunotherapies.The allergoid and MPL® adsorption to MCT in MATA-MPL allergy immunotherapy formulations was experimental determination using specific allergen IgE allerginicity and MPL® content methods. Binding forces between MPL® and MCT were investigated by competition binding experiments.MATA-MPL samples with different allergoids gave results within 100–104% of the theoretical 50μg/mL MPL® content. Unmodified drug substance samples showed significant desirable IgE antigenicity, 1040–170QAU/mL. MATA-MPL supernatant samples with different allergoids gave results of ≤2μg/mL MPL® and ≤0.1–1.4QAU/mL IgE antigenicity, demonstrating approximately ≥96 & 99% adsorption respectively. Allergoid and MPL® adsorption in different MATA-MPL allergy immunotherapy formulations is consistent and meets guideline recommendations. MCT formulations treated to disrupt electrostatic, hydrophobic and ligand exchange interactions, gave an MPL® content of ≤2μg/mL in supernatant samples. MCT formulations treated to disrupt aromatic interactions, gave an MPL® content of 73–92μg/mL in supernatant samples. MPL® adsorption to l-tyrosine in MCT formulations is based on interactions between the 2-deoxy-2-aminoglucose backbone on MPL® and aromatic ring of l-tyrosine in MCT, such as C–H⋯π interaction. MCT could be an alternative adjuvant depot for some infectious disease antigens.