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BACKGROUND: Study of the relationship between skin test results and IgE antibody levels is seriously hampered by the use of conventional allergen extracts because the precise amount of relevant allergen for each patient is unknown. OBJECTIVE: This study was designed to investigate skin reactivity with purified major allergens and to assess the relation with serum levels of IgE antibodies and to determine which additional factors contribute to the skin test result. METHODS: We used five purified major allergens Der p 1, Der p 2, Fel d1, Lol p1, and Lol p5 ) in skin tests, RASTs, and histamine release tests in 43 multisensitized patients with asthma or rhinitis. RESULTS: The differences in biologic activity of the five major allergens at a given level of specific IgE are within one order of magnitude. A significant residual variation remains in the correlation between skin test results and levels of IgE antibodies, which cannot be explained by imprecision of both tests (Pearson log skin test vs log specific IgE: r = -0.46-0.92). With similar levels of specific IgE, the amount of allergen that is required for a positive skin test result may differ by as much as a factor of 100 between patients. The amount of total IgE in serum contributes significantly to the skin test result. High values of total IgE are accompanied by a lower skin reactivity for allergen. Within individuals, allergens that cause skin test results that deviate from the prediction based on IgE antibody level often show a similar deviation in the histamine release test. This indicates that the type of IgE response (i.e., affinity or epitope recognition pattern) contributes significantly to the skin test result. Skin reactivity for histamine does not significantly influence the skin reactions expressed as allergen threshold. However, increased skin reactions with higher allergen dosages depend on histamine reactivity. CONCLUSION: The major allergens tested show similar biologic activities. In addition to IgE antibody level, total serum IgE and type of IgE antibody response contribute significantly to the skin test threshold for allergens. Even in a system with purified allergens, IgE antibody levels and skin test results are not interchangeable as an indicator of the degree of allergic sensitization.(J ALLERGY CLIN IMMUNOL 1996;97:16-25.)

BACKGROUND: In an outpatient population, a high frequency of positive skin prick test responses to dog dander was found in the absence of detectable IgE to dog dander in the RAST. The majority of these patients were sensitized to house dust mites(Dermatophagoides pteronyssinus)and had no obvious dog-related allergic symptoms. These findings prompted us to investigate whether dog dander skin test preparations are contaminated with house dust mite allergens in amounts sufficient to cause false-positive skin prick test responses in patients sensitized to house dust mites. METHODS: Antigen detection assays with monoclonal and polyclonal antibodies were used to determine concentrations of the major allergen Can f 1 from dog dander and the major allergens Der p 1 and Der p 2 from house dust mites in five commercially available dog dander skin prick test preparations (A to E). RESULTS: Can f 1 concentrations varied for the different extracts (A: 170 @mg/ml, B: 11.1 @mg/ml, C: 13.3 @mg/ml, D: 3.8 @mg/ml, and E: 59.4 @mg/ml). Der p 1 was detectable in all extracts (A: 33.4 ng/ml, B: 5.1 ng/ml, C: 29.6 ng/ml, D: 0.4 ng/ml, and E: 1.9 ng/ml), and Der p 2 was detectable in some of the commercially available dog dander skin prick test preparations tested (A: 31.3 ng/ml, B: 3.0 ng/ml, and C: 7.5 ng/ml). The median house dust mite threshold in the skin prick test was found to be 5.8 ng/ml of Der p 1 (range, 3.5 to 20.8 ng/ml) in nine patients tested. CONCLUSION: Contamination of commercially available dog dander skin prick test preparations with the major allergens (Der p 1 and Der p 2) of the house dust mite(D. pteronyssinus)was demonstrated. These contaminations cause false-positive responses to skin prick tests with dog dander in patients sensitized to house dust mite. (J Allergy Clin Immunol 1996;98:1028-34.)